Meteorologists love to describe temperatures in terms of “departures from normal.”” They will say, “Yesterday’s high was 69 (degrees), and that was one degree below normal.” (And that actually was Tuesday’s departure from normal, as officially measured at O’Hare.)
What’s left unsaid, however, is that a “normal” temperature is the 30-year average derived from the period 1971-2000, and that it is quite unusual for a day’s temperature to be right at “normal.” It’s even more unusual for two days to run at or near normal, but that is the pattern in which Chicago will find itself today and again Friday.
Chicago’s temps usually spend most of their time bouncing from well above normal to well below, and back again. Today’s “near normal” pattern breaks down over the weekend, when a warming trend sends readings to the upper 70s (9 (degrees) above normal) and into the lower 80s (14 (degrees) above) by this coming Tuesday.
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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.
