Dear Tom,
On Wednesday May 23 the National Weather service issued a Red Flag Warning for Chicago. How rare is this?
Craig Thayer, Chicago
Dear Craig,
Red Flag Warnings are issued to call attention to weather elements that result in conditions that could create a high fire danger. Though rarely issued here, they are quite common in the arid West when low humidity and high winds are forecast during an extended dry spell. Issuance criteria vary by region depending upon local climate and vegetation. In Chicago, the warnings are issued during prolonged dry periods when sustained winds are 20 m.p.h. or higher and the afternoon relative humidity is forecast to drop below 25%. On May 23, strong south winds gusted to more than 30 m.p.h. and the lowest afternoon R.H. was 23%. These factors, in combination with the recent dry conditions, prompted the rare Red Flag Warning for Chicago.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
