Temperatures hit the freezing mark in serveral areas around Chicago overnight, a little earlier than usual.
It got down to 31 in Rockford and Wheeling, 30 in Sterling, 29 in Valparaiso, 27 in West Chicago and a wintry 25 in Aurora, according to the National Weather Service.
Weather service outposts at airports in Gary, Waukegan, Midway and O'Hare all reported temperatures above 32.
The weather service had posted a freeze warning Sunday night for the Chicago area that expired at 9 a.m. this morning.
According to the weather service, the average date for the first freeze in Chicago – meaning at O'Hare – is Oct. 15. The earliest it has happened is Sept. 22, in 1995, and the latest is Nov. 24 , in 1931. Generally it's between Oct. 14 and 31.
The first killing freeze – denoted by the weather service as temperatures 28 degrees or lower -- happens on average on Oct. 27, the agency said. The earliest it has occurred was Oct. 2 in 1974, and the latest was Dec. 3 in 1899.
There's little chance that we'll get temperatures low enough for another warning the rest of this week.
According to the 7-day forecast from WGN-TV meteorologist Tom Skilling, temperatures will fall only as low as the high 30s or lows 40s the rest of the week, more like what you'd see in October than the weekend's November-like chills. Daytime highs are expected to get into the 60s most of the week, though winds today may make it feel cooler.
Chicago has been experiencing an abnormally warm and dry year, according to ChicagoWeatherCenter.com. 2012 is tied with 1921 for the warmest year in recorded history here with an average temperatures of 58.4 degrees. This year's precipitation is 20.91 inches, 72 percent of the normal 29.04 inches.