Meteorologists love to describe temperatures in terms of “departures from normal.” They will say, “Yesterday’s high was 69º, 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 (9º above normal) and into the lower 80s (14º above) by this coming Tuesday.
--By Richard Koeneman, WGN Weather Center Meteorologist
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
