The Midwest becomes the focus today for all the atmospheric ingredients necessary to
produce a major outbreak of severe weather: warm air and moisture streaming into the
region from the Gulf of Mexico, ample sunshine providing additional heating, a cold front
approaching from the west and a powerful jet stream surging overhead. The Storm
Prediction Center places Chicago in a 45-percent risk area today(45 percent chance of
severe weather in any given circle 50 miles in diameter.)
CHICAGO'S HOT WEATHER SEASON
A temperature of 90 degrees is the benchmark definition of a hot day. By that standard,
Chicago's "hot season" extends from April 10 (the date of the city's earliest-occurring
90-degree day) to Oct. 6 (the latest occur- rence. The city logs an annual average of 24
days at or above 90 degrees, and the average first occur- rence is on May 29.
--By Richard Koeneman, WGN Weather Center Meteorologist
