A prolonged and oppressive heat wave swept the Central Coast and Bay Area for almost a week from August 14th to August 19th with widespread record breaking temperatures observed across the region. This was caused by a strong high pressure system over the Desert Southwest that expanded westward into California. This dome of heat brought hot temperatures to the area for several days. Multiple days of triple digit afternoon highs were recorded inland with some coastal locations even reaching the mid 90s. Several days of hot and dry weather further dried fuels over the area increasing fire danger. During this event, a surge of monsoonal and tropical moisture from a former Tropical Storm advected northward with sufficient instability to generate multiple high based and dry thunderstorms that produced several thousand lightning strikes over the Greater Bay Area. Many locations saw wind gusts of 40-50 mph with isolated areas seeing gusts of 60-75 mph. This prompted the San Francisco Bay Area forecast office to issue a rare severe thunderstorm warning. These lightning strikes in combination with gusty and erratic outflow winds sparked hundreds of wildfires across the state of California. Several smaller fires combined to form complexes some of which are now among the largest wildfires in state history. Most of which were still actively burning at the end of August. Hundreds of thousands of acres have been burned with several hundred structures destroyed as well as a handful of deaths and injuries. Tens of thousands of residents were also forced to evacuate. Additionally, all of these wildfires burning simultaneously across the state gave the Bay Area the worst air quality in the world at one point.

Thunderstorm Wind in SANTA CLARA, CALIFORNIA
From 16-AUG-20 02:32:00 to 16-AUG-20 02:36:00 (PST-8)
Location: LOS GATOS
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Los Gatos station reported.

Thunderstorm Wind in SANTA CRUZ, CALIFORNIA
From 16-AUG-20 01:47:00 to 16-AUG-20 01:57:00 (PST-8)
Location: SWANTON
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station at Las Trancas.

Wildfire in NORTH BAY MOUNTAINS, CALIFORNIA
From 17-AUG-20 05:40:00 to 31-AUG-20 23:59:00 (PST-8)
Reported by: Fire Department/Rescue

A second round of thunderstorms moved through the region into the morning of August 17th producing additional lightning strikes over the Bay Area. On the early morning of the 17th lightning produced a fire in Napa County that became the Hennessey Fire. Eventually, this fire merged with several other fires across Napa, Sonoma, Solano, Yolo, and Lake Counties (Gamble, 15-10, Spanish, Markley, 13-4, 11-16, Walbridge) to form the LNU Lightning Complex https://www.fire.ca.gov/incidents/2020/8/17/lnu-lightning-complex-includes-hennessey-gamble-15-10-spanish-markley-13-4-11-16-walbridge/. Over 350,000 acres burned with over 200 structures damaged and over 1400 destroyed along with 5 fatalities (3 in Napa County and 2 in Solano County) including civilian and fire personnel across all counties. The LNU Lightning Complex Fire is now one of the top 5 largest wildfires in California state history. The fire was still burning at the end of August.

Thunderstorm Wind in SONOMA, CALIFORNIA
From 16-AUG-20 04:00:00 to 16-AUG-20 04:10:00 (PST-8)
Location: JIMTOWN
Magnitude: 60.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station (PG&E) reported gusts near Forest Lake.

Wildfire in SANTA CRUZ MOUNTAINS, CALIFORNIA
From 16-AUG-20 05:41:00 to 31-AUG-20 23:59:00 (PST-8)
Reported by: Fire Department/Rescue

On the morning of the 16th, lightning started multiple wildfires in Santa Cruz/San Mateo Counties that combined to form the CZU Lightning Complex https://www.fire.ca.gov/incidents/2020/8/16/czu-lightning-complex-including-warnella-fire/. At the end of August the fire had burned 84,640 acres, destroyed over 1100 buildings some of which were residential structures, injured three people (first responders), and killed another. Nearly 100,000 people were forced to evacuate. Historic Big Basin State Park sustained heavy damage from the fire burning down the parks headquarters. The fire was still actively burning at the end of August.

Lightning in SONOMA, CALIFORNIA
From 16-AUG-20 04:00:00 to 16-AUG-20 04:05:00 (PST-8)
Location: MARK WEST
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported lightning struck a redwood tree shearing off about 20 feet of it this morning.

Wildfire in COASTAL NORTH BAY INCLUDING POINT REYES NATIONAL SEASHORE, CALIFORNIA
From 18-AUG-20 13:27:00 to 31-AUG-20 23:59:00 (PST-8)
Property damage: 0.00K
Reported by: Fire Department/Rescue

Lightning sparked the Woodward Fire in the Point Reyes National Seashore in Marin County https://inciweb.nwcg.gov/incident/7062/. The fire was first reported on August 18th in an area of dense vegetation that is sparsely populated. Evacuations were ordered for surrounding areas, and a video from the National Seashore Visitor Center recorded a small fire whirl in the midst of the fire https://bit.ly/2RZb95x. No structures were damaged or destroyed.

Wildfire in EAST BAY HILLS AND THE DIABLO RANGE, CALIFORNIA
From 16-AUG-20 04:00:00 to 31-AUG-20 23:59:00 (PST-8)
Reported by: Fire Department/Rescue

After multiple lightning strikes across the region and breezy erratic winds, approximately 20 separate fires broke out across counties (Santa Clara, Alameda, Contra Costa, San Joaquin, and Stanislaus) the morning of August 16th. These fires were later re-named the SCU Lightning Complex Fires https://www.fire.ca.gov/incidents/2020/8/18/scu-lightning-complex/. This complex became one of the top 5 largest fires in California State history prompting numerous evacuations, destroying nearly 400,000 acres and destroying over 200 structures. These fires resulted in 6 injuries (Civilian and Fire Personnel). The fires came dangerously close to the historic Lick Observatory on Mount Hamilton https://arstechnica.com/science/2020/08/a-california-wildfire-nearly-destroyed-the-historic-lick-observatory/. The fire was still burning at the end of August.

Hail in MARIN, CALIFORNIA
From 17-AUG-20 05:03:00 to 17-AUG-20 05:08:00 (PST-8)
Location: ROSS
Magnitude: 0.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported rain, lightning, and hail. Hail size estimated.

Lightning in SAN MATEO, CALIFORNIA
From 16-AUG-20 04:15:00 to 16-AUG-20 04:20:00 (PST-8)
Location: REDWOOD CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Lightning struck a redwood tree in Redwood City https://sanfrancisco.cbslocal.com/2020/08/16/lightning-from-rare-bay-area-thunderstorm-leaves-damage-in-its-wake/.

Wildfire in SANTA LUCIA MOUNTAINS AND LOS PADRES NATIONAL FOREST, CALIFORNIA
From 16-AUG-20 13:56:00 to 31-AUG-20 23:59:00 (PST-8)
Reported by: Fire Department/Rescue

Lightning sparked the River Fire in Monterey County on the afternoon of the 16th https://www.fire.ca.gov/incidents/2020/8/16/river-fire/. The fire burned over 48,000 acres destroyed 30 structures and damaged 13. Several evacuation orders were issued throughout the month and four people including fire personnel and civilians were injured. Both the River and Carmel Fires caused smoke and ash to rain down on surrounding cities.  The fire was still burning at the end of August.

Lightning in MONTEREY, CALIFORNIA
From 15-AUG-20 10:15:00 to 15-AUG-20 10:20:00 (PST-8)
Location: SAN ARDO
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Report of lightning striking a tree near San Ardo sparking a small fire.

Lightning in SANTA CLARA, CALIFORNIA
From 16-AUG-20 07:00:00 to 16-AUG-20 07:05:00 (PST-8)
Location: SAN JOSE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Lightning struck two houses in San Jose, setting one on fire https://sanfrancisco.cbslocal.com/2020/08/16/lightning-from-rare-bay-area-thunderstorm-leaves-damage-in-its-wake/. Amount of damage unknown.

Wildfire in SANTA LUCIA MOUNTAINS AND LOS PADRES NATIONAL FOREST, CALIFORNIA
From 18-AUG-20 13:24:00 to 31-AUG-20 23:59:00 (PST-8)
Reported by: Fire Department/Rescue

A vegetation fire (Carmel Fire) broke out the afternoon of the 18th in Sky Ranch in Carmel Valley as a spot off the River Fire https://www.fire.ca.gov/incidents/2020/8/18/carmel-fire/. Multiple evacuations were ordered in the surrounding area with the fire ultimately destroying 73 structures and damaging 7. The combination of the Carmel and River fires rained down smoke and ash on surrounding cities. The fire was still burning at the end of August.

Hail in SONOMA, CALIFORNIA
From 17-AUG-20 07:01:00 to 17-AUG-20 07:06:00 (PST-8)
Location: SANTA ROSA
Magnitude: 0.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Video on twitter showing small hail in Santa Rosa.

Lightning in SANTA CLARA, CALIFORNIA
From 16-AUG-20 04:00:00 to 16-AUG-20 04:30:00 (PST-8)
Location: PALO ALTO
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Lightning struck a utility pole in Palo Alto early Sunday morning causing a small fire and causing about 4,500 customers to lose power https://www.paloaltoonline.com/news/2020/08/16/storm-brings-fires-power-outages-to-the-bay-area.

Rip Current in SAN FRANCISCO, CALIFORNIA
From 15-AUG-20 16:10:00 to 15-AUG-20 16:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Three teenagers were rescued in rough surf north of Sutro Baths and Ocean Beach in San Francisco https://www.sfgate.com/bayarea/article/Ocean-Beach-Sutro-Baths-surf-rescue-15487547.php. This occurred in the middle of a heat wave when a large number of people were headed to area beaches. SFFD reported 8 surf rescues that day.

Thunderstorm Wind in SANTA CLARA, CALIFORNIA
From 16-AUG-20 02:19:00 to 16-AUG-20 02:29:00 (PST-8)
Location: OLD GILROY
Magnitude: 40.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Tree down blocking roadway near Gilroy.

Excessive Heat in SANTA CLARA VALLEY INCLUDING SAN JOSE, CALIFORNIA
From 16-AUG-20 11:00:00 to 16-AUG-20 17:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Excessive heat across the region with widespread highs in the low 100s prompted 464 EMS calls across Santa Clara County.

Thunderstorm Wind in SANTA CRUZ, CALIFORNIA
From 16-AUG-20 01:47:00 to 16-AUG-20 01:57:00 (PST-8)
Location: BEN LOMOND
Magnitude: 40.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Strong winds blow down multiple trees in lower Glen Arbor.

Excessive Heat in SAN FRANCISCO BAY SHORELINE, CALIFORNIA
From 14-AUG-20 16:00:00 to 14-AUG-20 18:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Heat wave prompts rolling blackouts across the Bay Area https://abc7news.com/bay-area-heat-wave-rolling-blackouts-california-power-outage-san-francisco/6372015/. Timing estimated.

Thunderstorm Wind in SAN FRANCISCO, CALIFORNIA
From 16-AUG-20 02:50:00 to 16-AUG-20 03:00:00 (PST-8)
Location: SAN FRANCISCO
Magnitude: 47.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Observations in downtown San Francisco show multiple locations experiencing wind gusts over 50 mph.

Dense Smoke in SAN FRANCISCO, CALIFORNIA
From 19-AUG-20 07:00:00 to 19-AUG-20 22:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Smoke from multiple wildfires across California blanketed the Bay Area giving San Francisco the worst air quality in the world https://abc7news.com/smoke-forecast-bay-area-in-sf-today-air-pollution-wildfire/6377953/.

Thunderstorm Wind in ALAMEDA, CALIFORNIA
From 16-AUG-20 03:12:00 to 16-AUG-20 04:12:00 (PST-8)
Location: REDMONT CUT
Magnitude: 43.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Altamont RAWS station reported gusts.

Thunderstorm Wind in CONTRA COSTA, CALIFORNIA
From 16-AUG-20 02:50:00 to 16-AUG-20 03:00:00 (PST-8)
Location: WALNUT HGTS
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station at Shadowhawk reported wind gusts over 60 mph.

Thunderstorm Wind in MARIN, CALIFORNIA
From 16-AUG-20 02:50:00 to 16-AUG-20 03:00:00 (PST-8)
Location: SAUSALITO
Magnitude: 61.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet site (PG&E) near Sausalito recorded gusts at 70 mph.

Thunderstorm Wind in MONTEREY, CALIFORNIA
From 16-AUG-20 01:00:00 to 16-AUG-20 01:05:00 (PST-8)
Location: BIG SUR
Magnitude: 47.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station on Old Coast Tower road.

Thunderstorm Wind in NAPA, CALIFORNIA
From 16-AUG-20 04:29:00 to 16-AUG-20 04:39:00 (PST-8)
Location: YOUNTVILLE
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Atlas Peak station reported.

Thunderstorm Wind in SAN MATEO, CALIFORNIA
From 17-AUG-20 09:30:00 to 17-AUG-20 09:40:00 (PST-8)
Location: PACIFICA
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station on Lake Drive reported.