Chapter Hazard Analysis

Chicago Area Tornadoes by Hour

Source: Illinois State Water Survey



Chicago Area Tornadoes by Month

Source: Illinois State Water Survey
s seen in the chart below left, April, May, and June have the most frequent occurrences of tornadoes in the Chicago area. Tornadoes peak in the afternoon, when convectional heating is at a maximum. As shown in the chart below right, the peak time for tornadoes is at 5:00 p.m.

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Kane County Tornadoes Since 1950
Date	Time	Injuries	Fujita
April 28, 1955	2100	0	F1
August 23, 1956	1400	3	F1
August 23, 1956	1400	0	F2
August 06, 1958	1710	0	F2
August 03, 1960	1630	0	F1
April 11, 1965	1600	0	F1
April 19, 1966	2240	0	F1
April 21, 1967	1710	0	F2
June 09, 1974	1840	0	F0
June 20, 1974	1810	0	F0
June 07, 1980	1338	0	F0
July 16, 1980	0255	0	F2
May 15, 1982	1400	0	F0
May 05, 1991	1618	0	F1
July 02, 1993	1800	0	F0
May 28, 2003	PM	0	F0
Source: National Weather Service

istorical Events: In the past fifty years, Kane County has had 15 tornadoes. These are listed in the table to the right.

A detailed study of Chicago area tornadoes was conducted by the University of Chicago. The historical events are shown in Map 2-4. While this does not include all of Kane County, it does show that no area is safe from a twister.

The best known recent tornado in the area was the one that hit northwestern Will County on August 28, 1990. It was part of a storm that developed in Wisconsin at 12:00 p.m. At 1:42 a tornado was spotted northwest of Rockford. It was followed by a golf-ball size hail in Rockford and DeKalb County. At 3:30 the twister hit Plainfield and the Joliet area. The storm and high winds moved on into Indiana.

The tornado had winds up to 300 miles per hour, giving it a Fujita rating of F-5 (see box, previous page). It cut a path of destruction 20 miles long and from 200 yards to half a mile wide. Its impacts are highlighted on page 2-28.

In Kane County, storm damage was most severe at the Aurora airport, where winds of 94 mph were recorded. Planes were flipped over and hangers were damaged. The high winds toppled mature trees in Aurora.

Most of the damage, however, was to Will County and three schools in Plainfield. More than 1,200 homes and buildings and at least 50 businesses were damaged or destroyed. Damage to three schools in Plainfield left 1,600 students without classrooms. Luckily, the tornado hit after school had been let out, although there were some deaths among participants in after-school activities.

Map 2-4 and recent history make it appear that Kane County has no major threat from tornadoes. However, the County has been lucky. If the August 1990 tornado had struck 12 – 15 miles to the north and west, it would have hit the Aurora area where the higher concentration of development would probably have meant more deaths and destruction than what occurred in Will County.