December’s off to a very wintry start and likely to stay that way through the coming week. High temperatures the past three days have averaged 26.6°—a reading more than 13 degrees below normal. It’s been colder here this early in the season in only three previous years since 1930, including 1976, 1964 and 1942. With accumulating snow on the way expected to cover the ground, even colder readings lie ahead. The relationship between snow and cold weather is symbiotic. Snow reflects sunlight back to space before it can warm the atmosphere. And, at night, cooling occurs with special efficiency when a snowpack is in place. It’s a major reason lows dropped to a record-breaking -15° Friday at Huron and -13° at Sioux Falls—both in South Dakota—and why the season’s first single digits at O’Hare are likely Sunday night.
Highs stay in the teens or 20s the next 7 days. There’s never been a Dec. 1-9 period here which has failed to host at least one 30°.
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
