A long lived line of severe thunderstorms, known as a derecho, moved from Iowa into northern Illinois early in the morning of Saturday July 5. The storm caused widespread damage to trees and power lines in Ogle county. The most intense damage occurred in Winnebago county, as the storm cut a wide swath from Pecatonica to the west side of Rockford, through downtown Rockford, to the southeast side of the city and Cherry Valley. Near Pecatonica corn was flattened and trees were damaged. In Rockford, many large trees were uprooted or snapped. Many limbs and power lines were down. 80,000 customers were without power. A 731 foot TV tower and antenna was blown down by the wind near Meridian and Auburn Roads. The tower was valued at 1.5 to 2 million dollars. The storm also cost the city of Rockford over 1 million dollars in clean up of trees on city property. An annemometer on the west side of Rockford clocked a 104 mph wind gust. The storms also caused tree damage in Belvidere in Boone county, Crystal Lake in McHenry county, and Libertyville in Lake county. A 67 mph gust was measured in Libertyville. As the storms moved into the Chicago area, a well defined line developed and moved southeast through the metro area. High winds and tree damage were reported in Kane, DuPage and Cook counties. In Kane county a retired meteorologist reported 70 mph winds in St. Charles. In DuPage county trees were damaged in Lisle, Downers Grove and Clarendon Hills. The storm hit hard on the southwest side of Chicago from 44th and Marshfield, through Washington Park to Jackson Park at 63rd and the Lakefront. Large trees were blown down and buildings were damaged. Chicago emergency management officials reported nearly 500 trees downed or damaged, and 68 homes and businesses damaged, 8 of them uninhabitable. The roof was taken off a Park District building and a brick commercial building was destroyed. Stackable containers at a railroad yard were blown over. Damages to this area were estimated to be at least 5 million dollars. Winds were likely 90 mph or more. A wind gust to 88 mph was measured in Chicago Lawn with handheld equipment. Trees were also damaged in south suburban Midlothian.  A 90 foot tall, 3 foot diameter Oak tree that was estimated to be 273 years old, possibly the oldest tree in Chicago, was blown down.

Thunderstorm Wind in BOONE, ILLINOIS
From 05-JUL-03 03:40:00 to 05-JUL-03 03:45:00 (CST)
Location: BELVIDERE
Magnitude: 57 EG
Reported by: TRAINED SPOTTER

Thunderstorm Wind in MCHENRY, ILLINOIS
From 05-JUL-03 04:00:00 to 05-JUL-03 04:00:00 (CST)
Location: CRYSTAL LAKE
Magnitude: 52 EG
Reported by: TRAINED SPOTTER

Thunderstorm Wind in KANE, ILLINOIS
From 05-JUL-03 04:15:00 to 05-JUL-03 04:25:00 (CST)
Location: ST CHARLES
Magnitude: 61 EG
Reported by: METEOROLOGIST(NON NWS)

Thunderstorm Wind in OGLE, ILLINOIS
From 05-JUL-03 02:55:00 to 05-JUL-03 03:20:00 (CST)
Location: COUNTYWIDE
Magnitude: 57 EG
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in WINNEBAGO, ILLINOIS
From 05-JUL-03 03:10:00 to 05-JUL-03 03:30:00 (CST)
Location: PECATONICA
Magnitude: 90 MG
Property damage: 5M
Reported by: NWS STORM SURVEY

Thunderstorm Wind in COOK, ILLINOIS
From 05-JUL-03 04:20:00 to 05-JUL-03 04:45:00 (CST)
Location: LA GRANGE PARK
Magnitude: 78 EG
Property damage: 5M
Reported by: TRAINED SPOTTER

Thunderstorm Wind in LAKE, ILLINOIS
From 05-JUL-03 04:21:00 to 05-JUL-03 04:21:00 (CST)
Location: LIBERTYVILLE
Magnitude: 58 MG
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in DU PAGE, ILLINOIS
From 05-JUL-03 04:31:00 to 05-JUL-03 04:33:00 (CST)
Location: CLARENDON HILLS
Magnitude: 50 EG
Reported by: EMERGENCY MANAGER