A cluster of thunderstorms developed ahead of an approaching cold front across eastern Nebraska and western Iowa during the pre-dawn hours of August 10th. As a moist and highly unstable airmass fed into the system, the storms quickly intensified and began racing eastward as a derecho across Iowa into northern Illinois along a pre-existing boundary.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS ILX wrote it up.
A cluster of thunderstorms developed ahead of an approaching cold front across eastern Nebraska and western Iowa during the pre-dawn hours of August 10th. As a moist and highly unstable airmass fed into the system, the storms quickly intensified and began racing eastward as a derecho across Iowa into northern Illinois along a pre-existing boundary. While the greatest damage and highest wind speeds remained along and north of the I-80 corridor, a trailing boundary sank southward into central Illinois creating wind gusts of 60-75 mph. As a result, widespread wind damage was reported along and north of a Macomb...to Springfield...to Paris line.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Lincoln, IL wrote its last area forecast discussion before the first event at Aug 10, 12:04 PM CST, 56 minutes earlier.
Area Forecast Discussion National Weather Service Lincoln IL 104 PM CDT Mon Aug 10 2020 .SYNOPSIS... Issued at 339 AM CDT Mon Aug 10 2020 Hot and humid weather will prevail across central Illinois today...with the potential for strong to severe thunderstorms this afternoon and evening. High temperatures will top out in the upper 80s and lower 90s, while peak heat index values exceed 100 degrees. && .UPDATE... Issued at 1048 AM CDT Mon Aug 10 2020 Focus is on severe squall line currently pushing into central IA. Damaging wind gusts of 60-70 mph have already been reported with this system. Upscale growth is expected this afternoon as the downstream environment remains favorable. While deep layer shear is limited at 20-25 kt, high instability at 4-5k J/kg MLCAPE over central/southern IL will dominate the modest shear for an enhanced damaging wind threat. With the development of a rear inflow jet in central IA, an organized bow echo is likely to affect the northern parts of the CWA this afternoon. Potential is there for widespread damage resulting from 70+ mph wind gusts. System will likely track east/southeast along the northern edge of the max CAPE gradient, putting areas near/north of I-74 at greatest risk. Current timing suggests areas near GBG to be affected by 130 pm, and with the line tracking around 55 mph, exiting into Indiana by 4-5 pm. Very high rainfall rates will lead to a flash flood threat, though with the forward speed this may be more focused on urban areas. Ahead of the line, and to the south of areas affected, heat will be the other concern. Highs reaching the lower 90s will combine with dewpoints in the mid to upper 70s, for peak heat indices near 105F. && .SHORT TERM...(Today and tonight) ISSUED AT 339 AM CDT Mon Aug 10 2020 While the primary 850mb jet streak is currently oriented from Texas to Iowa, a weaker 20-30kt branch is noted on regional VAD data nosing into west-central Illinois. Despite short-wave ridging and the lack of a surface focusing mechanism, mid-level WAA associated with the jet will be enough to trigger widely scattered convection across the KILX CWA over the next few hours. These storms will track E/NE and will be primarily located along/east of I-57 by sunrise. Once this activity pushes into Indiana, a lull in precip chances will be noted from mid-morning through early afternoon, before attention turns to the development of strong to severe convection in advance of a cold front later in the day. The airmass ahead of the front will become very unstable, with HREF ensemble mean SBCAPES of 3000-4000J/kg. Despite favorable instability and synoptic lift associated with a vigorous short- wave pushing into the Great Lakes, deep-layer shear will remain weak...as evidenced by 0-6km bulk shear values of only around 20kt. Given the weak wind shear, the main severe weather threat this afternoon will be damaging wind gusts as a line of storms accelerates E/SE out of Iowa after 18z/1pm. While model solutions vary greatly, will be relying heavily upon the 06z HRRR which has performed quite well over the past couple of days. As a result, think the line of storms will arrive in the Illinois River Valley between 18z/1pm and 20z/3pm...then will track southeastward across the area and depart the far SE CWA after 02z/9pm. In addition to potentially damaging wind gusts, precipitable water values of 2.00-2.25 suggest the possibility of heavy rainfall and localized flash flooding. Before the storms arrive, afternoon high temperatures will rise into the upper 80s and lower 90s...with heat index values of 100-105 degrees. .LONG TERM...(Tuesday through Sunday) ISSUED AT 339 AM CDT Mon Aug 10 2020 00z Aug 10 models have continued the recent trend of pushing the cold front slightly further southward before it stalls...resulting in reduced rain chances. While there is still some uncertainty regarding the exact southern position of the front, it now appears likely that the northern half of the CWA will see mostly dry weather on Tuesday and Wednesday, with scattered showers/thunder persisting south of the I-72 corridor. The remnants of the front will then lift back northward by the end of the week, setting the stage for additional rain chances across the board Thursday through Sunday. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 104 PM CDT Mon Aug 10 2020 Main issue is timing severe squall line currently in eastern IA. This is expected to track east/southeast this afternoon, highest confidence for this to impact PIA/BMI/CMI from 19-23z. The line will be tracking quickly at around 60 kt, with similar wind speeds possible at the surface. Lower confidence that storms will impact SPI/DEC so only included tempo group here, where storms should be more scattered mid/late afternoon. After this window of active weather, VFR TAFs should prevail tonight through 18z. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && UPDATE...25 SYNOPSIS...Barnes SHORT TERM...Barnes LONG TERM...Barnes AVIATION...25
Hazardous Weather Outlook National Weather Service Lincoln IL 1140 AM CDT Mon Aug 10 2020 ILZ027>031-036>038-041>046-111645- Champaign-De Witt-Fulton-Knox-Logan-Marshall-Mason-McLean-Peoria- Piatt-Stark-Tazewell-Vermilion-Woodford- 1140 AM CDT Mon Aug 10 2020 This Hazardous Weather Outlook is for portions of central Illinois, east central Illinois and west central Illinois. .DAY ONE...THIS AFTERNOON AND TONIGHT... Thunderstorms are expected this afternoon and this evening. Widespread damaging wind gusts are possible with the storms this afternoon. Heavy rainfall could pose a flash flood threat, especially in urban areas. Hail is also possible in the strongest storms. The heat index is expected to climb between 100 to 105 degrees this afternoon. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY... Additional storms are possible from Wednesday through Saturday, mainly during the afternoon hours. These storms are currently not expected to be severe. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed between 1 pm and 6 pm. Please relay any information about observed severe weather to the National Weather Service while following all local, state and CDC guidelines. ILZ040-047>052-111645- Cass-Christian-Menard-Morgan-Sangamon-Schuyler-Scott- 1140 AM CDT Mon Aug 10 2020 This Hazardous Weather Outlook is for portions of central Illinois and west central Illinois. .DAY ONE...THIS AFTERNOON AND TONIGHT... Thunderstorms are expected this afternoon and this evening. A few of the storms may produce damaging wind gusts, hail, and heavy downpours. The heat index is expected to climb between 100 to 106 degrees this afternoon. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY... Additional storms are possible from Tuesday through Saturday, mainly during the afternoon hours. These storms are currently not expected to be severe. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed between 2 pm and 7 pm. Please relay any information about observed severe weather to the National Weather Service while following all local, state and CDC guidelines. ILZ053>057-061>063-111645- Clark-Coles-Cumberland-Douglas-Edgar-Macon-Moultrie-Shelby- 1140 AM CDT Mon Aug 10 2020 This Hazardous Weather Outlook is for portions of central Illinois and east central Illinois. .DAY ONE...THIS AFTERNOON AND TONIGHT... Thunderstorms are expected this afternoon and this evening. A few of the storms may produce damaging wind gusts, hail, and heavy downpours. The heat index is expected to climb between 99 to 105 degrees this afternoon. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY... Additional storms are possible from Tuesday through Saturday, mainly during the afternoon hours. These storms are currently not expected to be severe. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed between 3 pm and 8 pm. Please relay any information about observed severe weather to the National Weather Service while following all local, state and CDC guidelines. ILZ066>068-071>073-111645- Clay-Crawford-Effingham-Jasper-Lawrence-Richland- 1140 AM CDT Mon Aug 10 2020 This Hazardous Weather Outlook is for portions of southeast Illinois. .DAY ONE...THIS AFTERNOON AND TONIGHT... Thunderstorms are expected late this afternoon and this evening. A few of the storms may produce damaging wind gusts, hail, and heavy downpours. The heat index is expected to climb between 100 to 103 degrees this afternoon. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY... Additional storms are possible from Tuesday through Saturday, mainly during the afternoon hours. These storms are currently not expected to be severe. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed between 4 pm and 9 pm. Please relay any information about
The Quad Cities radar (KDVN), 76 km away, was scanning. The volume nearest the first event began at 18:57 UTC.
68 thunderstorm wind, 1 hail. Local standard time, as filed.
Numerous tree branches and power lines were blown down across Galesburg.
Several trees and power lines were blown down.
Several trees and power lines were blown down.
Several trees and power lines were blown down.
Several trees and power lines were blown down.
The roof of a greenhouse was damaged just west of Princeville.
A ten-inch diameter tree was blown across IL-78 near Graham Chapel Road.
A tree was blown onto a home at 4th Street and Birch Street and large tree branches were blown onto another home at 5th Street and Birch Street in Dunlap.
A tree was blown onto power lines.
A large tree was blown over in Kickapoo.
Several 8-inch diameter tree limbs were blown down.
An 8-inch diameter tree was blown onto a home on the 3300 block of Alta Lane.
A tree was snapped at its base in Canton.
A tree was blown onto a house.
The roof of a porch was blown off on the west side of Canton.
An 8-inch diameter tree was blown down.
A large billboard was blown over near the intersection of Gift Avenue and Sheridan Road. The steel beams supporting the sign were bent about halfway.
Several 8-inch diameter tree limbs were blown down at War Memorial Drive and Grave Avenue.
Thunderstorm winds damaged a home that was under construction.
Multiple tree limbs were blown down on the 5400 block of Galena Road.
A tree was blown onto a house in Chillicothe.
Several trees were blown into power lines in Rome.
A picnic shelter was destroyed.
Two trees were blown down, one of which blocked a roadway.
Part of the Germantown Hills Middle School roof was blown off.
Trees and power lines were blown down on 2nd Street.
A tree was blown onto a house on Main Street. Numerous 6 to 8-inch diameter tree branches were blown down around town. School Street was blocked by a fallen tree.
Two trees were snapped near the base.
Several trees and fences were blown down.
Multiple trees and power lines were blown down. One tree fell onto a house, and the residents had to be helped out of the house.
A tree was blown onto powerlines southwest of Bartonville.
Numerous 6-inch diameter tree branches were blown down throughout Canton.
A roof was blown off a large shed.
A tree was blown into power lines.
Two 10-inch diameter trees were blown down.
Several trees were blown down in Havana.
A tree was blown onto power lines on Fairview Drive.
A power pole was snapped near Jefferson Street and Westshore Drive.
Power lines were blown down in Eureka.
Several 6-inch diameter tree branches were blown down.
Multiple large tree limbs and power lines were blown down. Some streets were blocked by fallen trees.
A 1-foot diameter tree was blown down.
A grain bin was damaged.
A large tree was blown down across a road.
Several 10-inch diameter tree branches were blown down.
Downed power lines caused a 4-acre field fire northeast of Havana.
A large tree limb was blown down.
A large tree limb was blown down.
A large tree was blown down onto 2 homes near Constitution Trail.
A large tree branch was blown down along the east side of Hershey Street north of the Clearwater intersection.
A 4-inch diameter 18-foot long tree branch was blown down on Gill Street.
Numerous tree branches were blown down near Veteran's Road and Bloomington Road.
A power pole in the Ameren parking lot was blown onto a car. A 1-foot diameter tree limb fell onto another car.
Several power poles were damaged.
A partially rotten 36-inch diameter tree was blown over and knocked down power lines.
Power poles were blown down on South 9th Street.
An 18-inch diameter tree was blown over.
Two large trees were blown down, one of which fell onto a grain bin.
Power lines were blown down at 9th Street and Carpenter Street.
Several tree limbs were blown down in Le Roy.
A tree was blown down across a road.
A tree was blown onto a house in Blue Mound.
A 12-inch diameter tree branch was blown down.
Two large trees were blown down and shingles were damaged.
A tree was blown onto a house.
Two large trees were blown down onto US-150.
Numerous trees and power lines were blown down throughout Danville. Several streets were blocked.
Several large tree limbs were snapped.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2020Every state in 2020This day in weather historyWarnings in Illinois, August 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 914868, 914869, 914870, 914871, 914872, 918168, 914873, 914874, 918170, 914875, 914930, 914878, 914879, 914881, 914882, 914883, 914885, 914891, 914892, 914893, 918167, 918171, 914894, 914895, 914896, 914897, 914898, 914899, 914902, 914903, 918169, 914904, 914905, 914906, 914907, 914908, 914909, 914910, 914911, 914913, and more.