Wednesday’s unlimited sunshine 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 cloudburst. 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 moisture 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.
-By Tom Skilling, WGN-TV Chief Meteorologist
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
