Dear Tom,
I’ve heard that the amount of precipitation is around the same measurement each year. Since we’ve had such a dry summer, can we expect a wet fall and winter?
Katey Kinney, Crystal Lake, Ill.
Dear Katey,
On the contrary, Chicago’s precipitation totals exhibit great variability from normal values over periods as short as one year or from season to season. A dry summer does not mean a wet winter.
Chicago’s annual precipitation has averaged 34.11″ since 1871, but annual totals have ranged from 22.22″ (1962) to 49.35″ (1983).
Average annual precipitation does indeed change only very slowly over the long haul, but that requires the perspective of tens of years or longer.
History tells us that precipitation trends back toward normal values when droughts end, but the accumulated moisture deficits rarely are made up immediately.
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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.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
