It was a meteorological gift at a time of year better known for cold and snow. The level of warmth observed across the Chicago area Monday ranked among the rarest of the rare in December. Temperatures at 70-degrees and higher are exceedingly rare in December---it's happened only twice before on Dec. 3, 1970 (71-degrees) and Dec. 2, 1982 (71-degrees).
Further underscoring the rarity of such unseasonable warmth is the fact that of the possible 4,405 December days that are part of the city’s 142 year observational record, there have now been just 3 days on the books with temperatures at or above 70-degrees!
Chicago’s temperature reached the 70-degree mark at 2:14 pm at Midway Airport and at 2:44 pm at O’Hare.
Midway’s peak reading was to end up reaching 72-degrees, blowing past all of the South Side site’s previous highest December temperatures to become the month’s warmest on record since observations began there in 1928.
O’Hare’s official high, on the other hand, missed tying the date’s 71-degree record by a single degree and was 31-degrees above normal! And 70s weren’t limited to city observation sites. 64 of the 180 WeatherBug observation stations across northern Illinois and Indiana as well as southern Wisconsin and far southwest Lower Michigan---that’s 36 percent of the total---- registered readings at or above 70-degrees.
Warmest among them was 73-degrees at Wheaton and Pontiac; 71-degrees at Romeoville, University Park, Joliet and Chicago’s lakefront; and 70 at Riverside, Downer’s Grove, Aurora and Wheeling.
Warmth like Monday’s the equivalent of Chicago's normal late-September temps
Temperatures at Monday’s levels are usually found in the closing days of September—NOT the opening days of December. O’Hare’s 70-degree peak reading was the equivalent of the “normal high” on Sept. 27 and 28.
Record missed by just a degree
Had O’Hare's temperature risen a single degree above Monday’s 70-degree high, the 71-degree reading which resulted would have equaled the 1970 record for the date, which is also the month's warmest recorded temperature.
Abnormal warmth breaks records across 21 states
The huge pool of unseasonable warmth Monday set records across sections of 21 states from Nebraska to New Jersey. Among them were 83 Austin, TX; 75 Columbia, Missouri and Jonesboro, TN and 74 at Topeka, KS as well as both Kansas City and Springfield, MO.
Only moderate cooling before another temp rebound Thursday
Surprisingly, given how far into the new cold season we are, the downturn in temperatures Tuesday and Wednesday is to be modest---not extreme. The coldest air is to wait until next week to arrive.
Readings will be warming a bit Thursday and a moderately cool weekend is to follow.
Wintry storm prospects Sunday into Monday being monitored; more active pattern could be ahead next week
With the greater Chicago area still sadly short of moisture, having received just 61 percent of meteorological autumn’s typical precipitation (from September through November), the more active pattern which appears to be taking shape over the weekend and into next week may prove interesting and noteworthy.
There are hints low pressure will jump into the Plains and Midwest where it could initiate storm development over the weekend. This would make the track of the Sunday/Monday late weekend system potentially quite critical. Any shift in the trajectory of the storm track currently being forecast, could have a profound impact on the distribution of the weekend and early week’s precipitation and the form in which it falls.