A nearly stationary frontal boundary interacting with a moist environment triggered numerous clusters of strong to severe thunderstorms across north-central Illinois during the morning of August 12th.  Locally heavy rainfall resulted in flash flooding across portions of McLean and Champaign counties, while a few of the cells produced hail as large as quarters.  The activity eventually congealed into a linear structure, then began dropping southeastward across the remainder of central Illinois during the afternoon.  Several wind damage reports were received along the line as wind gusts frequently exceeded 60 mph.

Flash Flood in MCLEAN, ILLINOIS
From 12-AUG-21 09:00:00 to 12-AUG-21 14:00:00 (CST-6)
Location: ANCHOR
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Several rural roads across far southeastern McLean County were nearly impassible due to high water.

Flash Flood in SHELBY, ILLINOIS
From 12-AUG-21 16:57:00 to 12-AUG-21 18:15:00 (CST-6)
Location: MOWEAQUA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A quarter-mile stretch of a county road was under water southeast of Moweaqua.

Hail in MCLEAN, ILLINOIS
From 12-AUG-21 08:07:00 to 12-AUG-21 08:12:00 (CST-6)
Location: SAYBROOK
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in MCLEAN, ILLINOIS
From 12-AUG-21 08:17:00 to 12-AUG-21 08:22:00 (CST-6)
Location: LAURETTE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in MORGAN, ILLINOIS
From 12-AUG-21 16:30:00 to 12-AUG-21 16:35:00 (CST-6)
Location: MEREDOSIA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in MENARD, ILLINOIS
From 12-AUG-21 13:45:00 to 12-AUG-21 13:50:00 (CST-6)
Location: ATHENS
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several trees were blown down.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:40:00 to 12-AUG-21 13:45:00 (CST-6)
Location: LELAND GROVE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Trees were blown down at Iles Avenue and Leonard Street and at Leonard Street and Reed Avenue.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:47:00 to 12-AUG-21 13:52:00 (CST-6)
Location: RIVERTON
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A 16-inch diameter tree was snapped and several tree branches were blown down.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:48:00 to 12-AUG-21 13:53:00 (CST-6)
Location: SHERMAN
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A 3-foot diameter tree was broken at the base and numerous tree limbs were blown down.

Thunderstorm Wind in CHRISTIAN, ILLINOIS
From 12-AUG-21 14:10:00 to 12-AUG-21 14:15:00 (CST-6)
Location: OWANECO
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Several large tree branches up to 3 inches in diameter were blown down.  Some of them fell onto houses and vehicles.

Thunderstorm Wind in EFFINGHAM, ILLINOIS
From 12-AUG-21 15:20:00 to 12-AUG-21 15:25:00 (CST-6)
Location: TEUTOPOLIS
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several tree limbs were blown down.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:48:00 to 12-AUG-21 13:53:00 (CST-6)
Location: GRANDVIEW
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A power pole was snapped and tents were damaged at the Illinois State Fair.

Thunderstorm Wind in CHAMPAIGN, ILLINOIS
From 12-AUG-21 08:55:00 to 12-AUG-21 09:00:00 (CST-6)
Location: CHANUTE AFB
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Large tree limbs were blown down and a gas station sign was toppled.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 14:06:00 to 12-AUG-21 14:11:00 (CST-6)
Location: RIVERTON
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Several trees were blown over.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:39:00 to 12-AUG-21 13:44:00 (CST-6)
Location: SHERMAN
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Numerous trees, tree branches, and power lines were blown down in Sherman.

Thunderstorm Wind in CHRISTIAN, ILLINOIS
From 12-AUG-21 14:10:00 to 12-AUG-21 14:15:00 (CST-6)
Location: STONINGTON
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A few trees were snapped and several large tree limbs were blown down.

Thunderstorm Wind in SHELBY, ILLINOIS
From 12-AUG-21 14:38:00 to 12-AUG-21 14:43:00 (CST-6)
Location: TOWER HILL
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

The fire department was damaged, a metal roof was blown off a church, and a tree fell onto a car.

Thunderstorm Wind in SHELBY, ILLINOIS
From 12-AUG-21 14:50:00 to 12-AUG-21 14:55:00 (CST-6)
Location: SHELBYVILLE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A power pole was blown down.

Thunderstorm Wind in CHRISTIAN, ILLINOIS
From 12-AUG-21 14:15:00 to 12-AUG-21 14:20:00 (CST-6)
Location: TAYLORVILLE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Several tree branches were blown down on North Silver Street.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:44:00 to 12-AUG-21 13:49:00 (CST-6)
Location: MILDRED
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large tree limb was blown down on the north side of the interstate.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:44:00 to 12-AUG-21 13:49:00 (CST-6)
Location: STARNES
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large tree limb was blown down.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:48:00 to 12-AUG-21 13:53:00 (CST-6)
Location: CHATHAM
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A 1.5-foot diameter tree limb was blown down on Lakewood Drive near Sugar Creek Stables.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:48:00 to 12-AUG-21 13:53:00 (CST-6)
Location: TORONTO
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large tree was split and blown down south of Toronto Road on North Cotton Hill Road.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:27:00 to 12-AUG-21 13:32:00 (CST-6)
Location: CHATHAM
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several large tree branches were blown down.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:48:00 to 12-AUG-21 13:53:00 (CST-6)
Location: CHATHAM
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large tree was blown down in Bridgeview Park.

Thunderstorm Wind in SANGAMON, ILLINOIS
From 12-AUG-21 13:48:00 to 12-AUG-21 13:53:00 (CST-6)
Location: CHATHAM
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A few tree limbs were snapped and shingles were blown off a roof.