Wednesday’s unlimited sun-shine boosts to seven the number of consecutive rain-free days over much of the Chicago metro area, excluding sections of Lake, McHenry, Boone, Winnebago and northern Kane counties walloped by last Thursday night’s cloud-burst. Though subsoil moisture still has much of the region’s vegetation looking healthy and green, the period since May 1 has seen only 2.86″–far below the 137-year long-term average of 5.20″. That makes the period the 22nd driest on the books here since 1871. With June’s soil mois-ture loss to the atmosphere at the hands of evaporation in excess of 6″, any gap in rainfall results in rapid drying.
The build-up of ozone in recent days is behind the Air Pollution Action Day declared Wednesday. Ozone, which forms as a by-product when certain atmospheric pollutants are encouraged by sunlight to react, tends to peak in the afternoon and early evening hours.
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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.
