A powerful line of severe thunderstorms produced a derecho which tracked across eastern Iowa and northwest Illinois on the afternoon of Monday, August 10th, resulting in widespread straight line wind damage. The cost of damage from this storm was extreme, reaching an estimated 7.5 billion dollars along the path of these storms from Iowa through Illinois.  Two brief tornadoes have been confirmed within the widespread swath of wind damage, one just north of the Eastern Iowa Airport in Linn County Iowa, and one just south of Freeport, Illinois. These tornadoes have been designated as EF-U, as there was no observable damage directly attributable to the tornadoes from which an EF-scale rating could be assigned. While an average of two derechos a year occur across the area, a derecho of this intensity is a roughly once-in-a-decade occurrence. Another unusual aspect of this derecho was the duration of the strong winds, with gusts over 60 mph for over an hour at some locations.
The most extreme winds, estimated at 110-140 mph, destroyed or damaged numerous outbuildings, barns, grain bins, homes, mobile homes, apartment buildings, trees, and power poles in parts of Benton, Linn, Jones, Cedar, and Clinton Counties. The Cedar Rapids area was particularly hard hit. One fatality occurred in Linn County, as a tree fell on a cyclist. Several homes, apartment complexes, and businesses sustained damage consistent with 130-140 mph winds. Radio transmission towers in Marion and Clinton, Iowa collapsed due to winds estimated around 130 mph. Wind gusts of 80-100 mph were common as the line of storms moved through the Quad Cities area and then through northwest Illinois. A small pocket of winds estimated at 100-110 mph impacted Princeton, IL in Bureau County, where a 150 foot communications tower collapsed and numerous power poles were snapped. In addition to the damage, numerous long-duration power outages occurred across the region. Damage to crops was considerable along the derecho path. Numerous semi trucks were also blown off roadways along the path of the derecho.

Thunderstorm Wind in BENTON, IOWA
From 10-AUG-20 11:00:00 to 10-AUG-20 12:40:00 (CST-6)
Location: BELLE PLAINE ARPT
Magnitude: 126.00 MG
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Benton County, associated with a derecho. These winds lasted around an hour in total, even though the initial line of convection moved out fast. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were reported up to 80 mph for much of the county, with areas in central Benton County that had wind speed estimates from 120 mph wind or greater. The maximum measured unofficial wind gust was 126 mph in Atkins, IA. These estimates were determined based off damage surveys and photos submitted through social media. These strong winds extensively damaged most trees, powerlines, crops, and many structures in their path. This resulted in long duration power outages.

Tornado in LINN, IOWA
From 10-AUG-20 11:31:00 to 10-AUG-20 11:32:00 (CST-6)
Location: (CID)CEDAR RAPIDS AR
Tornado F-scale: EFU
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A brief tornado moved through cropland just north of the Eastern Iowa  Airport. The path was found in high resolution satellite imagery. The tornado was on the leading edge of a larger swath of straight line winds that snapped trees and destroyed outbuildings and grain bins. There was no damage directly attributable to the tornado from which an EF-scale rating could be assigned. Thus, the tornado is designated EF-U.

Thunderstorm Wind in IOWA, IOWA
From 10-AUG-20 11:00:00 to 10-AUG-20 12:30:00 (CST-6)
Location: VICTOR
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Iowa County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 60 to 80 MPH for much of the county, with areas in northern Iowa County that had wind speed estimates that were 80 MPH or higher. These estimates were determined based off damage reports and photos submitted through social media. These strong winds and duration extensively damaged most trees, powerlines, crops, and some structures in their path.  This also resulted in long duration power outages.

Thunderstorm Wind in KEOKUK, IOWA
From 10-AUG-20 11:00:00 to 10-AUG-20 12:30:00 (CST-6)
Location: DELTA
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Straight-line winds that produced damage were reported throughout Keokuk County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 60 to 80 MPH for much of the county. These estimates were determined based off damage reports. These strong winds and duration caused damage to trees, powerlines, and crops. This also resulted in long duration power outages.

Thunderstorm Wind in LINN, IOWA
From 10-AUG-20 11:30:00 to 10-AUG-20 12:50:00 (CST-6)
Location: COVINGTON
Magnitude: 122.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Linn County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 80 to 100 MPH for much of the county, with areas in central Linn County that had wind speed estimates that were 120 MPH or higher. The highest estimated wind speed were in the Cedar Rapids area where extensive damage to an apartment complex occurred with damage indicating winds about 140 MPH. A radio transmission tower also collapsed with wind speed estimated at 130 MPH. These estimates were determined based off damage reports and photos submitted through social media as well as a damage survey. The peak thunderstorm wind gust measured at the Cedar Rapids airport ASOS before it lost power was 68 MPH. The duration of strong winds caused extensive damaged most if not all trees, crops, and structures in their path. Due to the widespread damage, long duration power outages occurred. One fatality occurred here when a 63 year old man riding a bicycle was struck and killed by a tree that was knocked down due to the winds. There were also numerous injuries reported in the Cedar Rapids area.

Thunderstorm Wind in JOHNSON, IOWA
From 10-AUG-20 11:30:00 to 10-AUG-20 12:45:00 (CST-6)
Location: OXFORD
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Iowa County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 60 to 80 MPH for much of the county, with areas in northern Johnson County that had wind speed estimates that were 80 MPH or higher. These estimates were determined based off damage reports and photos submitted through social media. The peak wind gust measured at the Iowa City Airport was 69 MPH before the power went out. The duration of strong winds caused extensive damage to most trees, powerlines, crops, and structures in their path. The widespread damage also resulted in long duration power outages.

Thunderstorm Wind in WASHINGTON, IOWA
From 10-AUG-20 11:30:00 to 10-AUG-20 12:45:00 (CST-6)
Location: WEST CHESTER
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Washington County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 60 to 80 MPH. These estimates were determined based off damage reports and photos submitted through social media. The duration of strong winds caused extensive damage to some trees, powerlines, crops, and a few structures in their path. The widespread damage also resulted in long duration power outages.

Hail in DUBUQUE, IOWA
From 10-AUG-20 12:25:00 to 10-AUG-20 12:25:00 (CST-6)
Location: CASCADE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

This fell from storms just north of the track of the derecho path.

Thunderstorm Wind in HENRY, IOWA
From 10-AUG-20 11:51:00 to 10-AUG-20 12:00:00 (CST-6)
Location: MT UNION
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A healthy tree was split by thunderstorm winds.

Thunderstorm Wind in JEFFERSON, IOWA
From 10-AUG-20 11:58:00 to 10-AUG-20 12:08:00 (CST-6)
Location: FAIRFIELD
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Medium size tree limbs blown down by thunderstorm winds.

Thunderstorm Wind in DUBUQUE, IOWA
From 10-AUG-20 12:00:00 to 10-AUG-20 12:20:00 (CST-6)
Location: ASBURY
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

A very tall tree was topped off.

Thunderstorm Wind in DES MOINES, IOWA
From 10-AUG-20 12:24:00 to 10-AUG-20 12:34:00 (CST-6)
Location: DANVILLE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several 6 inch diameter tree branches were blown down, and across power lines.

Thunderstorm Wind in DES MOINES, IOWA
From 10-AUG-20 12:27:00 to 10-AUG-20 12:37:00 (CST-6)
Location: MEDIAPOLIS
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Numerous tree branches were blown down all over town.

Thunderstorm Wind in DES MOINES, IOWA
From 10-AUG-20 12:30:00 to 10-AUG-20 12:45:00 (CST-6)
Location: WEST BURLINGTON
Magnitude: 65.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several trees were blown down across a road.

Thunderstorm Wind in JEFFERSON, IOWA
From 10-AUG-20 11:35:00 to 10-AUG-20 11:35:00 (CST-6)
Location: FAIRFIELD MUNI ARPT
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

This was a measured wind gust from the south side of the derecho event.

Thunderstorm Wind in JEFFERSON, IOWA
From 10-AUG-20 11:50:00 to 10-AUG-20 11:50:00 (CST-6)
Location: FAIRFIELD
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter estimated 60 to 70 mph winds.

Thunderstorm Wind in HENRY, IOWA
From 10-AUG-20 11:55:00 to 10-AUG-20 11:55:00 (CST-6)
Location: MT PLEASANT MUNI ARP
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Measured at the airport at Mt. Pleasant.

Thunderstorm Wind in JONES, IOWA
From 10-AUG-20 11:50:00 to 10-AUG-20 13:15:00 (CST-6)
Location: MARTELLE
Magnitude: 78.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Jones County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 80 to 100 MPH for much of the county, with an area of 100  MPH or higher in the south central part of the county. These estimates were determined based off damage reports and photos submitted through social media. The duration of strong winds caused extensive damage to most trees, powerlines, crops, and structures in their path. The widespread damage also resulted in long duration power outages.

Thunderstorm Wind in DES MOINES, IOWA
From 10-AUG-20 12:22:00 to 10-AUG-20 12:22:00 (CST-6)
Location: BURLINGTON ARPT
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Measured at the Burlington Airport.

Thunderstorm Wind in CEDAR, IOWA
From 10-AUG-20 11:45:00 to 10-AUG-20 13:10:00 (CST-6)
Location: CEDAR BLUFF
Magnitude: 104.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Cedar County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 80 to 120 MPH for much of the county. These estimates were determined based off NWS Storm Surveys, damage reports and photos submitted through social media. The duration of strong winds caused extensive damage to most trees, powerlines, crops, and structures in their path. The widespread damage also resulted in long duration power outages.

Thunderstorm Wind in MUSCATINE, IOWA
From 10-AUG-20 11:50:00 to 10-AUG-20 13:08:00 (CST-6)
Location: NICHOLS
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Muscatine County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 60 to 70 MPH for much of the county with 80 MPH or higher over the northern half. These estimates were determined based off damage reports and photos submitted through social media. The duration of strong winds caused extensive damage to most trees, powerlines, crops, and structures in their path. The peak wind gust measured at the Muscatine Airport was 58 MPH before power was lost. The widespread damage also resulted in long duration power outages.

Thunderstorm Wind in LOUISA, IOWA
From 10-AUG-20 11:50:00 to 10-AUG-20 13:10:00 (CST-6)
Location: COTTER
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced damage were reported throughout Louisa County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be around 60 MPH for much of the county. These estimates were determined based off damage reports and photos submitted through social media. The duration of strong winds caused extensive damage to a few trees and crops in their path.

Thunderstorm Wind in JACKSON, IOWA
From 10-AUG-20 12:15:00 to 10-AUG-20 13:40:00 (CST-6)
Location: MONMOUTH
Magnitude: 78.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Jackson County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 60 to 80 MPH for much of the county with winds of 80 to 100 MPH across the southern two thirds of the county These estimates were determined based off damage reports. The duration of strong winds caused extensive damage to trees, powerlines, crops, and structures in their path. The widespread damage also resulted in long duration power outages.

Thunderstorm Wind in CLINTON, IOWA
From 10-AUG-20 12:10:00 to 10-AUG-20 13:40:00 (CST-6)
Location: TORONTO
Magnitude: 113.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread straight-line winds that produced extensive damage were reported throughout Clinton County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 80 to 100 MPH for much of the county with winds over 100 MPH in the city of Clinton. These estimates were determined based off damage reports and photos submitted through social media. The Clinton Airport AWOS reported a peak gust of 74 MPH with winds over 60 MPH for 45 minutes. In addition, a radio transmission tower collapsed at KMCN in Clinton with significant damage to the roof.  The wind speed estimate with transmission tower collapse was 130 MPH.   The duration of strong winds caused extensive damage to most trees, powerlines, crops, and structures in their path. The widespread damage also resulted in long duration power outages.

Thunderstorm Wind in SCOTT, IOWA
From 10-AUG-20 12:10:00 to 10-AUG-20 13:40:00 (CST-6)
Location: NEW LIBERTY
Magnitude: 78.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Widespread straight-line winds that produced extensive damage were reported throughout Scott County, associated with a derecho. These winds lasted around an hour in total at any one location, even though the initial line of storms moved out quickly. Damaging straight-line winds continued and were associated with the rear inflow jet. Maximum wind speeds were estimated to be 80 to 100 MPH for much of the county. These estimates were determined based off damage reports and photos submitted through social media. The peak wind speed measured at the Davenport Airport ASOS was 86 MPH before the power went out with several large tree limbs and trees blown down on the airport property, including at the NWS Weather Forecast Office in the Quad Cities. The duration of strong winds caused extensive damage or loss to most trees, powerlines, crops, and some roof damage in their path. The widespread damage also resulted in long duration power outages.