A severe thunderstorm complex raced southward across southern Illinois during the early evening hours. Widespread wind damage occurred with this long-lived complex, which met the definition of a derecho. This convective system took shape over the Missouri/Iowa border region and then progressed south-southeast to the Tennessee Valley by late evening. A very moist and unstable air mass set the stage for this derecho. Surface dew points were near 80 degrees, with mixed-layer capes over 4000 j/kg. When the atmosphere is that unstable, wind shear does not need to be particularly strong for significant severe weather to occur. The bulk wind shear in the 0 to 6 km layer averaged 20 to 30 knots. Deep northerly wind flow averaged around 20 knots from 850 to 500 mb on the front side of a high pressure ridge.

Thunderstorm Wind in JOHNSON, ILLINOIS
From 28-JUN-18 18:32:00 to 28-JUN-18 18:47:00 (CST-6)
Location: GOREVILLE
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Widespread wind damage occurred around the county. Numerous trees and power lines were down, causing power outages. A tree landed on a home near Buncombe. Sheriff officials requested residents to stay off the roads due to the amount of tree damage.

Thunderstorm Wind in GALLATIN, ILLINOIS
From 28-JUN-18 18:35:00 to 28-JUN-18 18:45:00 (CST-6)
Location: OMAHA
Magnitude: 65.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread wind damage occurred across the county. Numerous trees and power lines were down. The roof was blown off the county high school.

Thunderstorm Wind in POPE, ILLINOIS
From 28-JUN-18 18:40:00 to 28-JUN-18 18:55:00 (CST-6)
Location: DELWOOD
Magnitude: 56.00 EG
Property damage: 35.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Widespread damaging winds occurred around the county. Numerous trees and power lines were down, causing power outages. Several trees blocked Highway 145 in northern parts of the county.

Thunderstorm Wind in MASSAC, ILLINOIS
From 28-JUN-18 18:54:00 to 28-JUN-18 19:09:00 (CST-6)
Location: NEW COLUMBIA
Magnitude: 65.00 EG
Property damage: 70.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Widespread damaging winds occurred across the county. Numerous trees and power lines were down. The roof was lifted off a business in Metropolis. Trees landed on some structures, including a carport near Brookport, a trailer near Round Knob, and a house in Metropolis.

Hail in FRANKLIN, ILLINOIS
From 28-JUN-18 16:35:00 to 28-JUN-18 16:35:00 (CST-6)
Location: SESSER
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash Flood in PERRY, ILLINOIS
From 28-JUN-18 18:35:00 to 28-JUN-18 19:45:00 (CST-6)
Location: DU QUOIN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

There were numerous reports of flash flooding on several county roadways throughout the county. In Pinckneyville, water was up to the bottom of the door of a truck on a flooded street.

Thunderstorm Wind in JEFFERSON, ILLINOIS
From 28-JUN-18 17:45:00 to 28-JUN-18 18:00:00 (CST-6)
Location: DIX
Magnitude: 56.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread wind damage occurred around the county, mostly due to downed trees. Power outages were reported throughout the county.

Thunderstorm Wind in PERRY, ILLINOIS
From 28-JUN-18 17:50:00 to 28-JUN-18 18:05:00 (CST-6)
Location: TAMAROA
Magnitude: 65.00 EG
Property damage: 60.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread wind damage occurred across the county. Multiple trees were down, causing numerous power outages. Some entire towns were in the dark, including Tamaroa. At least one tree landed on a structure.

Thunderstorm Wind in WAYNE, ILLINOIS
From 28-JUN-18 17:50:00 to 28-JUN-18 18:05:00 (CST-6)
Location: ZENITH
Magnitude: 65.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Widespread damaging winds occurred across western parts of the county, mainly west of Fairfield. A wind gust to 75 mph was measured by a personal weather station at Wayne City.

Thunderstorm Wind in FRANKLIN, ILLINOIS
From 28-JUN-18 18:00:00 to 28-JUN-18 18:15:00 (CST-6)
Location: SESSER
Magnitude: 65.00 EG
Property damage: 70.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread wind damage occurred across the county. Multiple power poles were down.  A downed power pole on State Highway 154 at Rend Lake trapped a person in a vehicle. Numerous trees and power lines were down, causing power outages. Trees up to two feet in diameter were down in Benton.

Tornado in WILLIAMSON, ILLINOIS
From 28-JUN-18 18:12:00 to 28-JUN-18 18:13:00 (CST-6)
Location: JOHNSTON CITY
Tornado F-scale: EF0
Property damage: 35.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A brief weak tornado occurred, with peak winds estimated near 85 mph. Two garage buildings were blown off their foundations. Numerous trees were uprooted or snapped. Several shingles were blown off a roof. An eyewitness reported watching the tornado destroy the garage buildings and then continue on the ground a few hundred yards.

Thunderstorm Wind in WILLIAMSON, ILLINOIS
From 28-JUN-18 18:15:00 to 28-JUN-18 18:30:00 (CST-6)
Location: HERRIN
Magnitude: 65.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Widespread wind damage occurred throughout the county. Numerous trees and power lines were down, causing widespread power outages. Some structural damage was reported, mainly due to trees falling on structures. Shingles were blown off a roof in Carterville. A boat dock was damaged at Lake of Egypt, near the Johnson County line.

Thunderstorm Wind in JACKSON, ILLINOIS
From 28-JUN-18 18:16:00 to 28-JUN-18 18:31:00 (CST-6)
Location: ELKVILLE
Magnitude: 65.00 EG
Property damage: 60.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Widespread wind damage occurred across the county. Multiple trees were down, causing widespread power outages. A wind gust to 67 mph was recorded by the automated observing system at the Southern Illinois Airport near Carbondale. Power poles were down. Some roads were blocked by downed trees, including Old Route 13.

Thunderstorm Wind in SALINE, ILLINOIS
From 28-JUN-18 18:20:00 to 28-JUN-18 18:35:00 (CST-6)
Location: GALATIA
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Widespread wind damage occurred across the county. Numerous trees and power lines were down, causing widespread power outages. A large tree blocked Route 34, and a sign was blown apart at the Harrisburg-Raleigh Airport.

Thunderstorm Wind in WHITE, ILLINOIS
From 28-JUN-18 18:25:00 to 28-JUN-18 18:30:00 (CST-6)
Location: ENFIELD
Magnitude: 56.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Widespread wind damage occurred in southern and western parts of the county. Multiple trees were blown down. A tree landed on a house in Norris City.