# 2020 Western United States wildfire season

"none" is preferred when the title is sufficiently descriptive; see [[WP:SDNONE]]
The Western United States experienced a series of major wildfires in 2020. Severe August thunderstorms ignited numerous wildfires across California, Oregon, and Washington, followed in early September by additional ignitions across the West Coast. Fanned by strong, gusty winds and fueled by hot, dry terrains, many of the fires exploded and coalesced into record-breaking megafires, burning more than 10.2 million acres (41,000 square kilometres) of land, mobilizing tens of thousands of firefighters, razing over ten thousand buildings, and killing at least 37 people. The fires caused over $19.884 billion (2020 USD) in damages, including $16.5 billion in property damage and $3.384 billion in fire suppression costs. Climate change and poor forest management practices contributed to the severity of the wildfires.

## Background
### Fire, environment, and cultural shift

Save for areas along the Pacific coast and mountain ridgetops, North America tends to be wetter in the east and drier in the west. This creates ideal conditions in the West for lightning sparked and wind driven storms to spread large-scale, seasonal wildfires. Human societies practicing cultural burns developed in these conditions. Various Indigenous controlled fire practices, as well as their adoption by settlers, were curtailed and outlawed during the European colonization of the Americas, culminating with the modern fire suppression era, signified by the Weeks Act of 1911, which formalized paradigmatic changes in ecosystem priorities and management. Land was protected from fire, and vegetation accumulated near settlements, increasing the risk of explosive, smoky conflagrations.
Many indigenous tribes, including the Karuk, have passed down cultural memories of adaptations to fire-prone ecosystems, including cultural burning. In the last few decades, these have been acknowledged by the United States Forest Service, NOAA, and other agencies in American colonial nations.
While lightning sparked ignitions are typical of fire-prone ecosystems, higher human population and increased development in the wildland–urban interface has increased accidental and intentional sparking of destructive fires.

### Record hemispheric heat

   The Northern Hemisphere January–August land and ocean surface temperature tied with 2016 as the warmest such period since global records began in 1880. The Southern Hemisphere had its third-warmest such period (tied with 2017) on record, behind 2016 and 2019.
Record dry weather struck the Western United States in late 2019, extending all the way through the winter of 2020. The lack of precipitation prompted concerns from state governments and the press. On March 22, a state of emergency was declared by California Governor Gavin Newsom due to a mass die-off of trees throughout the state, potentially increasing the risk of wildfire. Oregon officially declared the start of their wildfire season that same month. Despite light rain in late March and April, severe drought conditions persisted, and were predicted to last late into the year, due to a delayed wet season. After fires began in Washington in April, several more fires occurred throughout the West Coast, prompting burn ban restrictions in Washington and Oregon, come July.

### Year-to-date wildfire figures

United States agencies stationed at the National Interagency Fire Center in Idaho maintain a "National Large Incident Year-to-Date Report" on wildfires, delineating 10 sub-national areas, aggregating the regional and national totals of burn size, fire suppression cost, and razed structure count, among other data. As of October 21, "Coordination Centers" of each geography report the following:
Note: Check primary sources for up-to-date statistics. This data is not final and may contain duplicate reports until the data is finalized around January 2021.
| Coordination Center | Acres | Hectares | Suppression Costs | Structures Destroyed |
| Alaska Interagency | 171,045.7 | 69,219.7 | $14,837,241.00 | 8 |
| Northwest Area | 1,930,877.2 | 781,398.3 | $414,535,531.13 | 4,472 |
| Northern California Area | 4,058,314.2 | 1,642,341.5 | $1,388,359,480.14 | 9,747 |
| Southern California Area | 1,318,498.5 | 533,577.4 | $921,427,069.00 | 1,857 |
| Northern Rockies | 368,164.6 | 148,990.9 | $75,698,682.00 | 222 |
| Great Basin | 926,042.5 | 374,756.1 | $251,845,657.39 | 275 |
| Southwest Area | 1,047,410.6 | 423,872.0 | $204,076,181.96 | 64 |
| Rocky Mountain Area | 1,011,332.6 | 409,271.8 | $343,972,034.34 | 1,140 |
| Eastern Area | 14,989.8 | 6,066.2 | $631,398.58 | 24 |
| Southern Area | 2,892,799.1 | 1,170,674.3 | $15,526,190.92 | 324 |
| Totals | 13,739,474.8 | 5,560,168.2 | $3,630,909,466.46 | 18,133 |
* ↑ Year-to-date totals as of December 30, 2020

## Timeline of events
### Initial ignitions and weather conditions

April saw the beginning of wildfires in the west coast, as Washington experienced two fires: the Stanwood Bryant Fire in Snohomish County (70 acres (28 ha)) and the Porter Creek Fire in Whatcom County (80 acres (32 ha)). The Oregon Department of Forestry declared fire season beginning July 5, 2020, signaling the end of unregulated debris burning outdoors, a major cause of wildfires.
Between July 16 and 30, the Washington State Department of Natural Resources (DNR) and many county governments – including Mason, Thurston, King, Pierce and Whatcom Counties – issued fire safety burn bans due to elevated risk of uncontrolled fires. In late July, a brush fire in Chelan County, the Colockum Fire, burned at least 3,337 acres (1,350 ha) and caused homes to be evacuated. A fire on the Colville Reservation near Nespelem called the Greenhouse Fire burned at least 5,146 acres (2,083 ha) and caused the evacuation of the Colville Tribal Corrections Facility and other structures.
Between August 14 and 16, Northern California was subjected to record-breaking warm temperatures, due to anomalously strong high pressure over the region. Early on August 15, the National Weather Service for San Francisco issued a Fire Weather Watch highlighting the risk of wildfire starts due to the combination of lightning risk due to moist, unstable air aloft, dry fuels, and hot temperatures near the surface. Later that day, the Fire Weather Watch was upgraded to a Red Flag Warning, noting the risk of abundant lightning already apparent as the storms moved toward the region from the south.
In mid-August, the remnants of Tropical Storm Fausto interacted with the jet stream, resulting in a large plume of moisture moving northward towards the West Coast of the U.S., triggering a massive siege of lightning storms in Northern California, and setting the conditions for wildfires elsewhere. Due to abnormal wind patterns, this plume streamed from up to 1,000 miles (1,609 km) off the coast of the Baja Peninsula into Northern California. This moisture then interacted with a high-pressure ridge situated over Nevada that was bringing a long-track heat wave to much of California and the West. These colliding weather systems then created excessive atmospheric instability that generated massive thunderstorms throughout much of Northern and Central California. Multiple places also experienced Midwest-style convective "heat bursts"–in which rapid collapse of thunderstorm updrafts caused air parcels aloft to plunge to the surface and warm to extreme levels, with one location near Travis Air Force Base going from around 80 to 100 °F (27 to 38 °C) in nearly 1–2 hours. Additionally, much of these storms were only accompanied with dry lightning and produced little to no rain, making conditions very favorable for wildfires to spark and spread rapidly.
As a result of the fires, on August 19, Governors Kate Brown and Jay Inslee declared a state of emergency for Oregon and Washington respectively.

### Growth of fires

By August 20, the Palmer Fire near Oroville, Washington – which started August 18 – had reached 13,000 acres (5,300 ha) and forced evacuation of up to 85 homes. The largest of the fires in the Olympics reached 2.4 acres (0.97 ha) by August 20.
The Evans Canyon Fire, a few miles north of Naches, began around August 31 and expanded to tens of thousands of acres, shut down Washington State Route 821 in the Yakima River Canyon, burned several homes and caused hundreds of families to evacuate, and caused unhealthy air quality in Yakima County. By September 6, it had burned almost 76,000 acres (31,000 ha).
The August 2020 lightning fires include three of the largest wildfires in the recorded history of California: the SCU Lightning Complex, the August Complex, and the LNU Lightning Complex. On September 10, 2020, the August Complex became the single-largest wildfire in the recorded history of California, reaching a total area burned of 471,185 acres (1,907 km$^2$). Then, on September 11, it merged with the Elkhorn Fire, another massive wildfire of 255,039 acres (1,032 km$^2$), turning the August Complex into a monster wildfire of 746,607 acres (3,021 km$^2$).
In early September 2020, a combination of a record-breaking heat wave, and Diablo and Santa Ana winds sparked more fires and explosively grew active fires, with the August Complex surpassing the 2018 Mendocino Complex to become California's largest recorded wildfire. The North Complex increased in size as the winds fanned it westward, threatening the city of Oroville, and triggering mass evacuations. During the first week in September, the 2020 fire season set a new California record for the most area burned in a year at 2,000,000 acres (810,000 ha). As of September 13, 3,200,000 acres (1,300,000 ha) had burned in the state. On September 5, heat from the Creek Fire generated a large pyrocumulonimbus cloud, described as one of the largest seen in the United States.
On September 7, a "historic fire event" with high winds resulted in 80 fires and nearly 300,000 acres (120,000 ha) burned in a day. Malden, in the Palouse Country of Eastern Washington, was mostly destroyed by one of the fires. By the evening of September 8, the Cold Springs Canyon and adjacent Pearl Hill Fires had burned over 337,000 acres (136,000 ha) and neither was more than 10% contained. Smoke blanketed the Seattle area on September 8 and caused unhealthy air conditions throughout the Puget Sound region, and affected Southwest British Columbia.
On September 8, 2020, in Salem, Oregon, dark red skies as a result of smoke were visible beginning in the late morning. On September 9, 2020, San Francisco and Eureka, California were similarly affected, with dark orange skies reported.
The cities of Phoenix and Talent in Oregon were substantially destroyed by the Almeda Drive Fire. State-wide, at least 23 people have been killed. On September 11, authorities said they were preparing for a mass fatality incident. As of September 11, 600 homes and 100 commercial buildings have been destroyed by the Almeda Drive Fire. Officials stated that the Almeda Drive Fire was human-caused. On September 11, a man was arrested for arson, for allegedly starting a fire that destroyed multiple homes in Phoenix and merged with the Almeda Drive Fire. A separate criminal investigation into the origin point of the Almeda Drive Fire in Ashland is ongoing.
Around September 11–12, wildfires were starting to encroach upon the Clackamas County suburbs of Portland, Oregon, especially the fast-moving Riverside Fire which had already jumped the nearby community of Estacada, but shifting wind directions kept the fire away from the main Portland area.
Through much of September, at least 8 large wildfires, each of 100,000 acres (400 km$^2$) or more, were burning in Washington and Oregon, with 3 in Washington and 5 in Oregon. This was unprecedented for those two states, which combined only saw a total of 26 large fires from 1997 to 2019. On September 22, 10 large fires, each of at least 100,000 acres, were burning across California, including 5 of the 10 largest wildfires in the state's history.

### Evacuations

The first evacuations began on September 4, when almost 200 people were airlifted out of the Sierra National Forest due to the rapidly exploding Creek Fire. Then on September 9, most of the southern area of the city of Medford, Oregon was forced to evacuate and almost all of the 80,000 residents living in the city were told to be ready if necessary because of the uncontained Almeda Drive Fire, which was fast encroaching on their city. As of September 11, about 40,000 people in Oregon had been instructed to evacuate, and 500,000, accounting for about 10% of the state's population, had received instructions to prepare for evacuation, being under a Level 1, 2, or 3 fire evacuation alert.

## List of wildfires

The following is a list of fires that burned more than 1,000 acres (405 ha) or produced significant structural damage or casualties.
| Name | County | Acres | Start date | Containment date | Notes |
| Interstate 5 | Kings County, California | 2,060 | May 3 | May 7 | |
| PCMS Complex | Las Animas County, Colorado | 2,175 | May 16 | May 21 | Unknown Cause |
| Cherry Canyon | Las Animas County, Colorado | 11,818 | May 20 | May 27 | Lightning-Caused |
| Range | San Luis Obispo County, California | 5,000 | May 27 | May 28 | |
| Tabby Canyon | Tooele County, Utah | 13,378 | May 30 | June 2 | Caused by exploding target. Merged with North Stansbury Fire on June 1 at 6,848.8 acres. |
| Scorpion | Santa Barbara County, California | 1,395 | May 31 | June 1 | |
| Bighorn | Pima County, Arizona | 119,987 | June 5 | July 23 | Burned on the Santa Catalina Mountains |
| Quail | Solano County, California | 1,837 | June 6 | June 10 | 3 structures destroyed |
| Farm Camp | San Miguel County, New Mexico | 22,872 | June 6 | June 14 | Lightning-Caused |
| Tadpole | Grant County, New Mexico | 11,159 | June 6 | July 17 | Lightning-Caused |
| Wood | San Diego County, California | 11,000 | June 8 | June 12 | Burned on Camp Pendleton |
| India | San Diego County, California | 1,100 | June 8 | June 14 | Burned on Camp Pendleton |
| Mangum | Coconino County, Arizona | 71,450 | June 8 | July 7 | Burned in the Kaibab National Forest |
| Soda | San Luis Obispo County, California | 1,672 | June 10 | June 11 | 2 structures destroyed |
| Grant | Sacramento County, California | 5,042 | June 12 | June 17 | 1 structure damaged |
| Bush | Gila County, Maricopa County, Arizona | 193,455 | June 13 | July 6 | Human-Caused |
| East Canyon | La Plata County, Montezuma County, Colorado | 2,905 | June 14 | June 27 | Lightning-Caused |
| Vics Peak | Socorro County, New Mexico | 14,624 | June 15 | August 4 | Lightning-Caused;burned in the Apache Kid Wilderness |
| Walker | Calaveras County, California | 1,455 | June 16 | June 20 | 2 structures destroyed |
| Grade | Tulare County, California | 1,050 | June 22 | June 26 | |
| Brown | White Pine County, Nevada | 8,268 | June 24 | June 30 | The cause of the wildfire is still under investigation |
| Poeville | Washoe County, Nevada | 2,975 | June 26 | July 6 | Led to evacuation of portions of the City of Reno |
| Wood Springs 2 | Apache County, Arizona | 12,861 | June 27 | July 11 | Lightning-Caused; 7 structures destroyed on the Navajo Nation |
| Canal | Millard County, Juab County, Utah | 78,065 | June 27 | July 13 | Lightning-Caused; destroyed 34 structures; 100% contained on June 27 but escaped containment due to strong winds |
| Pass | Merced County, California | 2,192 | June 28 | June 30 | |
| Bena | Kern County, California | 2,900 | July 1 | July 3 | |
| Polles | Gila County, Arizona | 628 | July 3 | July 23 | Lightning-Caused; a helicopter supporting firefighting efforts crashed on July 7, taking the life of pilot Bryan Boatman.The incident is under investigation. |
| Crews | Santa Clara County, California | 5,513 | July 5 | July 13 | 1 structure destroyed; 1 damaged; 1 injury. Resulted in evacuations of rural Gilroy. |
| Soledad | Los Angeles County, California | 1,525 | July 5 | July 15 | 1 injury |
| Numbers | Douglas County, Nevada | 18,380 | July 6 | July 14 | 40 buildings destroyed |
| Mineral | Fresno County, California | 29,667 | July 13 | July 26 | 7 structures destroyed |
| Coyote | San Benito County, California | 1,508 | July 15 | July 18 | |
| Hog | Lassen County, California | 9,564 | July 18 | August 8 | 2 structures destroyed |
| Gold | Lassen County, California | 22,634 | July 20 | August 8 | 13 structures destroyed; 5 structures damaged; 2 firefighters injured in burnover |
| July Complex 2020 | Modoc County, Siskiyou County, California | 83,261 | July 22 | August 7 | 1 structure destroyed; 3 outbuildings destroyed |
| Blue Jay | Mariposa County, Tuolumne County, California | 6,922 | July 24 | November 19 | Lightning-sparked |
| Red Salmon Complex | Humboldt County, Siskiyou County, Trinity County, California | 144,698 | July 26 | November 23 | Originally started as both the Red and Salmon fire (both started by lightning strikes), but have since merged into one fire |
| Chikamin | Chelan County, Washington | 1,685 | July 31 | September 24 | |
| Apple | Riverside County, California | 33,424 | July 31 | November 16, 2020 | 4 structures destroyed; 8 outbuildings destroyed; 4 injuries |
| Pond | San Luis Obispo County, California | 1,962 | August 1 | August 8 | 1 structure destroyed; 1 damaged; 13 outbuildings destroyed |
| North | Lassen County, California | 6,882 | August 2 | August 10 | 6,882 acres in total, of which approximately 4,105 acres burned in Washoe County, Nevada |
| Stagecoach | Kern County, California | 7,760 | August 3 | August 16 | 23 structures destroyed; 4 damaged; 25 outbuildings destroyed; 2 damaged; 1 firefighter fatality |
| Neals Hill | Harney County, Oregon | 3,391 | August 5 | August 20 | Caused by lightning |
| Bumble Bee | Yavapai County, Arizona | 2,993 | August 7 | August 12 | Human-Caused |
| Wolf | Mariposa County, Tuolumne County, California | 2,057 | August 11 | November 19 | Lightning-sparked |
| Lake | Los Angeles County, California | 31,089 | August 12 | October 5 | Lightning-sparked, 33 structures destroyed; 6 damaged; 21 outbuildings destroyed; 2 injuries |
| Ranch 2 | Los Angeles County, California | 4,237 | August 13 | October 5 | Lightning-sparked |
| Hills | Fresno County, California | 2,121 | August 15 | August 24 | Lightning-sparked; 1 fatality |
| Loyalton | Lassen County, Plumas County, Sierra County, California | 47,029 | August 15 | September 14 | Lightning-sparked, Caused National Weather Service to issue first ever Fire Tornado Warning; 5 homes, 6 outbuildings destroyed |
| Beach | Mono County, California | 3,780 | August 16 | August 28 | Lightning-sparked |
| Frog | Crook County, Oregon | 4,020 | August 16 | September 1 | Caused by lightning |
| Green Ridge | Deschutes County, Oregon | 4,338 | August 16 | September 1 | Caused by lightning |
| River | Monterey County, California | 48,088 | August 16 | September 4 | Lightning-sparked; 30 structures destroyed; 13 structures damaged; 4 injuries |
| Dome | San Bernardino County, California | 43,273 | August 16 | September 14 | Lightning-sparked, Burned in the Mojave National Preserve |
| Indian Creek | Malheur County, Oregon | 48,128 | August 16 | September 16 | Caused by lightning |
| CZU Lightning Complex | San Mateo County, Santa Cruz County, California | 86,509 | August 16 | September 22 | Several lightning-sparked fires burning close together across San Mateo and Santa Cruz Counties; 1,490 structures destroyed; 140 structures damaged; 1 injury; 1 fatality. |
| SCU Lightning Complex | Santa Clara County, Alameda County, Contra Costa County, San Joaquin County, Merced County, Stanislaus County, California | 396,624 | August 16 | October 1 | Deer Zone, Marsh, Canyon Zone and other surrounding fires combined into one multi-fire incident by CalFire; all believed to have been sparked by an intense and widespread lightning storm; 222 structures destroyed; 26 structures damaged; 6 injuries. It is the third-largest fire complex in California history. |
| Beachie Creek | Linn County, Oregon | 193,573 | August 16 | October 28. Merged with the Lionshead Fire and became the Santiam Fire on September 8. | |
| August Complex | Glenn County, Mendocino County, Lake County, Tehama County, Trinity County, California | 1,032,648 | August 16 | November 12 | Lightning strikes started 37 fires, several of which grew to large sizes, especially the Doe Fire; 935 structures destroyed; 2 firefighter injuries; 1 firefighter fatality. It became the largest fire complex in California history and combined with the Elkhorn Fire on September 10. |
| Lionshead | Jefferson County, Oregon | 204,469 | August 16 | December 10. Merged into the Beachie Creek Fire and became the Santiam Fire on September 8. | |
| Rattlesnake | Tulare County, California | 8,419 | August 16 | December 18 | Lightning sparked a slow-growing fire in inaccessible terrain. |
| Downey Creek | Douglas County, Oregon | 2,570 | August 16 | December 31 | |
| Jones | Nevada County, California | 705 | August 17 | August 28 | Lightning sparked, 21 structures destroyed, 3 structures damaged, 7 injuries |
| Holser | Ventura County, California | 3,000 | August 17 | September 6 | |
| Sheep | Plumas County, Lassen County, California | 29,570 | August 17 | September 9 | Lightning-sparked, 26 structures destroyed, 1 injury |
| LNU Lightning Complex | Colusa County, Lake County, Napa County, Sonoma County, Solano County, Yolo County, California | 363,220 | August 17 | October 2 | Multi-fire incident that includes the Hennessey Fire (305,651 acres), the Walbridge Fire (55,209 acres), and the Meyers Fire (2,360 acres) sparked by lightning; 1,491 structures destroyed; 232 structures damaged; 5 injuries; 5 fatalities. It is the fourth-largest fire complex in California history. |
| Butte/Tehama/Glenn Lightning Complex (Butte Zone) | Butte County, California | 19,609 | August 17 | October 17 | Lightning sparked 34 fires throughout Butte County; 14 structures destroyed; 1 structure damaged; 1 injury |
| White River | Wasco County, Oregon | 17,383 | August 17 | October 20 | |
| North Complex | Plumas County, Butte County, Yuba County, California | 318,935 | August 17 | December 4 | Lightning strikes, includes the Claremont Fire and the Bear Fire; 2,357 structures destroyed, 114 structures damaged; 15 fatalities; 2 injuries; It is the sixth-largest fire complex in California history. |
| Salt | Calaveras County, California | 1,789 | August 18 | August 24 | Lightning-sparked |
| Carmel | Monterey County, California | 6,905 | August 18 | September 4 | Lightning-sparked, 73 structures destroyed; 7 structures damaged |
| W-5 Cold Springs | Lassen County, Modoc County, California | 84,817 | August 18 | September 14 | Lightning-sparked. Fire spread eastward into Washoe County, Nevada. |
| Palmer | Okanogan County, Washington | 17,988 | August 18 | December 1 | |
| Laurel | Wheeler County, Oregon | 1,257 | August 19 | September 14 | |
| Woodward | Marin County, California | 4,929 | August 18 | October 1 | Lightning-sparked |
| Dolan | Monterey County, California | 124,924 | August 18 | December 31 | Cause not officially determined; however, a suspect was charged with arson in connection to the fire |
| SQF Complex | Tulare County, California | 174,178 | August 19 | January 5 | Lightning-sparked, contains the Castle Fire and the Shotgun Fire |
| Moc | Tuolumne County, California | 2,857 | August 20 | August 30 | Lightning-sparked |
| East Fork | Duchesne County, Utah | 89,765 | August 21 | November 5 | Lightning-Caused; destroyed 11 structures and merged with the Phinney Lake fire at 10,040 acres |
| Moraine | Tulare County, California | 1,316 | August 21 | December 18 | Lightning-sparked |
| Slink | Mono County, California | 26,759 | August 29 | November 8 | Lightning-sparked |
| Evans Canyon | Kittitas County, Washington | 75,817 | August 31 | October 31 | |
| Creek | Fresno County, Madera County, California | 379,895 | September 4 | December 24 | 853 structures destroyed, 64 structures damaged; 29 injuries; 1 fatality |
| Valley | San Diego County, California | 16,390 | September 5 | September 24 | 51 structures destroyed, 11 structures damaged, 2 injuries |
| El Dorado | Riverside County, San Bernardino County, California | 22,744 | September 5 | November 18 | Sparked by a pyrotechnic device at a gender reveal party. 20 structures destroyed, 4 structures damaged; 13 injuries, 1 fatality |
| Cold Springs | Okanogan County, Washington | 189,923 | September 6 | September 30 | 1 fatality |
| Bobcat | Los Angeles County, California | 115,796 | September 6 | October 19 | Unknown cause, 170 structures destroyed, 47 structures damaged; 6 Injuries |
| Oak | Mendocino County, California | 1,100 | September 7 | September 14 | Unknown cause, 25 structures destroyed, 20 structures damaged |
| P-515 | Jefferson County, Oregon | 4,609 | September 7 | December 10. Merged into the Lionshead Fire on September 8. | |
| Slater/Devil | Siskiyou County, Del Norte County, California, Josephine County, Oregon | 157,229 | September 7 | November 16 | 2 fatalities, 1 structure destroyed |
| Two Four Two | Klamath County, Oregon | 14,473 | September 7 | October 31 | |
| Brattain | Lake County, Oregon | 50,951 | September 7 | October 31 | |
| Holiday Farm | Lane County, Oregon | 173,393 | September 7 | October 31 | 1 fatality |
| Echo Mountain Complex | Lincoln County, Oregon | 2,552 | September 7 | October 27 | 293 structures destroyed, 22 structures damaged |
| Babb-Maiden/Manning | Spokane County, Washington | 18,254 | September 7 | December 15 | |
| Whitney | Lincoln County, Washington | 127,430 | September 7 | December 18 | |
| Inchelium Complex | Ferry County, Washington | 19,399 | September 7 | September 28 | |
| Pearl Hill | Douglas County, Washington | 223,730 | September 7 | December 15 | Started when the Cold Springs fire jumped the Columbia River, then spread quickly due to strong winds and low relative humidity. Destroyed 25 residences and 35 other structures. |
| Apple Acres | Chelan County, Washington | 5,500 | September 7 | December 15 | |
| Fork | El Dorado County, California | 1,673 | September 8 | November 9 | |
| South Obenchain | Jackson County, Oregon | 32,671 | September 8 | October 31 | |
| Riverside | Clackamas County, Oregon | 138,054 | September 8 | December 3 | |
| Santiam | Clackamas County, Jefferson County, Linn County, Marion County, Wasco County, Oregon | 402,592 | September 8 | December 10 | Includes the Lionshead, Beachie Creek, and P-515 Fires, which merged. 1568+ structures destroyed, 5 deaths |
| Big Hollow | Skamania County, Washington | 24,995 | September 8 | December 1 | |
| Almeda Drive | Jackson County, Oregon | 3,200 | September 8 | September 15 | 2457+ structures destroyed, 3 fatalities |
| Chehalem Mountain- Bald Peak | Washington County, Oregon | 2,000 | September 8 | September 14 | |
| Thielsen | Douglas County, Oregon | 9,975 | September 9 | November 16 | |
| Willow | Yuba County, California | 1,311 | September 9 | September 14 | 41 structures destroyed; 10 structures damaged |
| Archie Creek | Douglas County, Oregon | 131,542 | September 9 | November 16 | |
| Bullfrog | Fresno County, California | 1,185 | September 9 | November 9 | |
| Fox | Trinity County, California | 2,188 | September 14 | November 1 | |
| Snow | Riverside County, California | 6,254 | September 17 | November 18 | |
| Glass | Napa County, California Sonoma County, California | 67,484 | September 28 | October 21 | 1,555 structures destroyed, 282 structures damaged |
| Zogg | Shasta County, California | 56,338 | September 28 | October 13 | 204 structures destroyed, 27 structures damaged; 1 injury, 4 fatalities |
| Range | Utah County, Utah | 3,496 | October 17 | November 11 | Human-Caused (Cause: Police Target Shooting) |
| Silverado | Orange County, California | 12,466 | October 26 | November 7 | 5 structures destroyed, 9 structures damaged; 2 injuries |
| Blue Ridge | Orange County, California | 13,694 | October 26 | November 7 | 1 structure destroyed, 10 structures damaged |
| Laura 2 | Orange County, California | 2,800 | November 17 | November 24 | 40 structures destroyed |
| Mountain View | Mono County, California | 20,385 | November 17 | November 27 | 90 structures destroyed, 8 damaged; 1 fatality |
| Airport | Riverside County, California | 1,087 | December 1 | December 12 | |
| Bond | Orange County, California | 6,686 | December 2 | December 10 | Started by a house fire; 31 structures destroyed; 21 structures damaged; 2 firefighter injuries |
| Sanderson | Riverside County, California | 1,933 | December 13 | December 14 | |
| Creek 5 | San Diego County, California | 4,276 | December 23 | December 31 | Unknown cause; over 7,000 people evacuated from housing areas on Camp Pendleton |

## Causes
### Fire policy

Prior to development, California fires regularly burned significantly more acreage than in recent history. Wildfires have been aggressively suppressed in the last century, resulting in a buildup of fuel, increasing the risk of large uncontrollable fires. There is broad scientific consensus that there should be more controlled burning of forest in California in order to reduce fire risk. Controlled burning is hampered by wildfire litigation models that present wildfires in court cases as the result of careless ignition events while discounting underlying forest conditions. A 2020 ProPublica investigation blamed the culture of Cal Fire, greed on the part of fire suppression contractors, and risk aversion on the part of the U.S. Forest Service from preventing appropriate controlled burns from taking place.

### Climate change

Climate change has led to increased heat waves and the risk of drought in California, creating the conditions for more frequent and severe wildfires. It has been observed that since the early 1970s, warm-season days in California warmed by ca. 1.4 °C. This significantly increases the atmospheric vapor pressure deficit, the difference between the actual and a maximum moisture content for a certain temperature. Trends simulated by climate models are consistent with human-induced trends. Summer forest-fire area reacts to the vapor pressure deficit exponentially, i.e., warming has grown increasingly impactful.
David Romps, director of the Berkeley Atmospheric Sciences Center summarizes the situation as follows: "To cut to the chase: Were the heat wave and the lightning strikes and the dryness of the vegetation affected by global warming? Absolutely yes. Were they made significantly hotter, more numerous, and drier because of global warming? Yes, likely yes, and yes." Similarly, Friederike Otto, acting director of the University of Oxford Environmental Change Institute states, "There is absolutely no doubt that the extremely high temperatures are higher than they would have been without human-induced climate change. A huge body of attribution literature demonstrates now that climate change is an absolute game-changer when it comes to heat waves, and California won't be the exception." Susan Clark, director of the Sustainability Initiative at the University at Buffalo, states, "This is climate change. This increased intensity and frequency of temperatures and heat waves are part of the projections for the future. [...] There is going to be more morbidity and mortality [from heat.] There are going to be more extremes."

### Arson

In August 2020, a suspect was charged by the Monterey County Sheriff with arson relating to the Dolan Fire; however, this has not been officially determined as the cause of the fire. In April 2021, another suspect, already arrested and charged for the murder of a woman, was charged with arson relating to the Markley Fire, one of the wildfires involving in the LNU Lightning Complex fires; according to authorities, the fire was set to cover up the aforementioned murder. Arson has also been suspected as the cause of the Ranch 2 Fire in Los Angeles County.

## Obstacles to fire control
### Rumors about political extremist involvement

In Oregon, rumors spread that Antifa activists allegedly involved in arson and rioting accompanying the nearby George Floyd protests in Portland, Oregon, were deliberately setting fires and were preparing to loot property that was being evacuated. Some residents refused to evacuate based on the rumors. Authorities urged residents to ignore the rumors and follow evacuation orders, noting that firefighters' lives could be endangered rescuing those who remained. QAnon followers participated in spreading the rumors, with one claim that six antifa activists had been arrested for setting fires specifically amplified by "Q", the anonymous person or people behind QAnon.
False rumors also circulated that members of far-right groups such as the Proud Boys had started some of the fires. However, authorities labelled the claims as false, saying that people needed to question claims they found on social media.
There have been a number of arrests for arson surrounding the wildfires, but there is no indication that the incidents were connected to a mass arson campaign, according to multiple law enforcement officers. For example, a man allegedly set fires in Glide, Oregon, after a Douglas Forest Protection Association member refused to give him a ride to town.

### COVID-19 pandemic

The COVID-19 pandemic brought new challenges for firefighters fighting wildfires due to measures intended to reduce the transmission of the disease. The California Department of Forestry and Fire Protection (CAL Fire) implemented new protocols such as wearing face masks and maintaining social distancing while resting, and reducing the number of occupants in the pickup trucks used to transport firefighters.
California relies heavily on inmate firefighters, with incarcerated people making up nearly a quarter of CAL FIRE's total workforce in 2018–2019. Coronavirus measures within the prison system, such as early release and quarantine policies, have reduced the number of inmate firefighters available, necessitating the hiring of additional seasonal firefighters.

## Impacts
### Fire

In Oregon, wildfires throughout the whole year, with most occurring in September, charred a record of 1,000,000 acres (4,000 km$^2$), destroying a total of 4,800 structures, including 1,145 homes, and killing 9 people. The towns of Phoenix and Talent were mostly destroyed in the Almeda fire on September 8. In Washington, 2020 wildfires burned 800,000 acres (3,200 km$^2$), with 418 structures, including 195 homes, burned. In California, about 3,300,000 acres (13,000 km$^2$) burned from wildfires in 2020, the highest burned acreage ever recorded in a fire season. About 2,100,000 acres (8,500 km$^2$) burned in the August lighting wildfires and 1,000,000 acres (4,000 km$^2$) more in September. 4,200 structures were destroyed the whole year in California, and 25 people were killed.

### Smoke and air pollution

The fires resulted in worsened air pollution across much of the western U.S. and Canada, from Los Angeles to British Columbia. Alaska Airlines suspended its flights from Portland, Oregon, and Spokane, Washington, due to poor air quality. Some cities in Oregon recorded air quality readings of over 500 on the AQI scale, while readings of over 200 were recorded in major cities. Smoke from the fires were carried to the East Coast and Europe, causing yellowed skies but having little impact on air quality.
The heavy smoke had resulted in several smoke-related incidents. In California, for example, a San Francisco resident was hiking through Yosemite National Park on September 5 when suddenly the sky turned a dark, ugly color and the temperature dropped greatly, reminiscent of a thunderstorm. Ash and smoke started falling, and this erratic weather was caused by the nearby Creek Fire. In another incident, on September 14, an Oakland A's player was at a game at the Seattle Mariners' stadium, when suddenly in the middle of the game he started gasping for air.
It is estimated that as many as 1,200 to 3,000 indirect deaths have been caused by the adverse effects of smoke inhalation.
Red skies appeared over many cities over the West Coast, including on Orange Skies Day, due to smoke from the wildfires blocking lighter colors, created from light infraction. Due to the complex oxidative chemistry occurring during the transport of wildfire smoke in the atmosphere, the toxicity of emissions was suggested to increase over time.
* Smoke from the North Complex Fire settles over San Francisco, turning the midday sky a dark orange on September 9
* Smoke over Portland, Oregon on September 9
* Air pollution obscuring the skyline of Seattle, Washington on September 11
* Haze in the upper atmosphere of New York City on September 16

### Ecological effects

The unique sagebrush scrub habitat of the Columbia Basin in Washington was heavily affected by the fires, devastating populations of the endemic Columbia Basin pygmy rabbit and endangered, isolated populations of greater sage-grouse and Columbian sharp-tailed grouse. About half of the pygmy rabbit population and over 30-70% of the grouse population may have been lost to the fires, reversing decades of conservation work. Aside from climate change, the spread of the fires may have been assisted by the intrusion of invasive cheatgrass into the habitats. Fires in old-growth forests of Oregon may negatively affect the populations of the endangered northern spotted owl and pine marten, and the resulting ash from the fires may be washed into streams and threaten endangered salmon. Climate change also reduces the likelihood of forests re-establishing themselves after a fire.
The Cassia Crossbill may lose half its population due to the pending consequences of the wildfires, one of which engulfed a large portion of the South Hills, one of the only two strongholds for the bird.