On the evening of July 9th, intense thunderstorms developed rapidly along a warm front draped from northwest to southeast across the area. There were two rounds of thunderstorms, the first being discrete, rotating storms called supercells. These supercell thunderstorms dropped large hail across portions of western Illinois (Mt. Sterling area) and also across the western St. Louis metro area. Hail in excess of 2 inches was noted in both of these supercells. Over time, the storms congealed into a large complex of thunderstorms known as a mesoscale convective complex (MCC). This line of storms contained damaging, sometimes destructive winds as they quickly pushed southeast across east-central Missouri into southwest Illinois. The worst damage was noted from Rensselaer, MO southward to Perry, MO, where straight-line winds of 90 mph were found. This same line of storms also affected the St. Louis metro area, bringing widespread 60-70 mph winds across the metro causing many large tree limbs to fall and many to be without power.

Thunderstorm Wind in CALHOUN, ILLINOIS
From 09-JUL-21 22:33:00 to 09-JUL-21 22:33:00 (CST-6)
Location: MICHAEL
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm winds blew down several large trees near Michael.

Thunderstorm Wind in MADISON, ILLINOIS
From 09-JUL-21 23:56:00 to 09-JUL-21 23:56:00 (CST-6)
Location: MADISON
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ST. CLAIR, ILLINOIS
From 10-JUL-21 00:02:00 to 10-JUL-21 00:02:00 (CST-6)
Location: (CPS)EAST STL ARPT C
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm Wind in ST. CLAIR, ILLINOIS
From 10-JUL-21 00:29:00 to 10-JUL-21 00:29:00 (CST-6)
Location: (BLV)SCOTT AFB BELLE
Magnitude: 62.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Thunderstorm Wind in ST. CLAIR, ILLINOIS
From 10-JUL-21 00:50:00 to 10-JUL-21 00:50:00 (CST-6)
Location: ST LIBORY
Magnitude: 61.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm winds blew down a 1 foot in diameter tree branch in town.

Hail in RANDOLPH, ILLINOIS
From 10-JUL-21 01:06:00 to 10-JUL-21 01:06:00 (CST-6)
Location: ELLIS GROVE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BROWN, ILLINOIS
From 09-JUL-21 19:48:00 to 09-JUL-21 20:20:00 (CST-6)
Location: MT STERLING
Magnitude: 2.75 
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail up to baseball size fell over Mt. Sterling and surrounding areas causing widespread damage to several dozen vehicles, buildings and crops. At least one farmer lost about a 1000 acres of corn and soybeans due to the large hail.

Thunderstorm Wind in BROWN, ILLINOIS
From 09-JUL-21 19:50:00 to 09-JUL-21 20:20:00 (CST-6)
Location: MT STERLING
Magnitude: 70.00 EG
Property damage: 300.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Widespread wind damage from the north side of Mt. Sterling to south of Hersman. Numerous trees, tree limbs, power poles and power lines were blown down.  Several businesses and homes, especially on the south side of Mt. Sterling, sustained roof damage from fallen trees and tree limbs. One of the baseball dugouts at the high school was destroyed, with other minor damage around the school campus. A couple of trees fell onto unoccupied vehicles causing major damage.

Thunderstorm Wind in PIKE, ILLINOIS
From 09-JUL-21 20:36:00 to 09-JUL-21 20:58:00 (CST-6)
Location: PERRY
Magnitude: 61.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A wide swath of damaging winds from Perry southward into Griggsville and Valley City. Numerous trees, tree limbs and power lines were blown down. Some of the trees fell onto Illinois Route 107 both north and south of Perry. A power pole was blown down in Griggsville.