Chicagoans haven’t experienced a lower September afternoon relative humidity reading in 17a years. Thursday afternoon’s 20% at 2:45 p.m. became the city’s second lowest relative humidity ever recorded in a September. A 16% relative humidity on September 9, 1988 stands as the month’s lowest reading since records began here in 1871. The incredibly low moisture content of the air was behind the day’s unlimited visibilities and a daytime temperature surge to 85°—the 57th reading at or above 85° this year. By comparison, temperatures through September 1 last year had reached or exceeded 85° only 19 times.
Hints of autumn were to be found early Thursday in the Plains and eastern Rockies. A morning low of 36° at Chadron, Nebraska set a new record for the date while Craig, Colorado residents shivered in a 27° morning chill.
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
