Polar air has been noticeably absent most of this winter season. Since climatological winter began on December 1st, only 7 of the past 38 days have posted a temperature deficit. Our last sub-normal reading occurred December 10th. Snowfall has also been meager, with 1.6 inches recorded at O’Hare International Airport. The city has had no observed snow cover since December 1st. The opening week of January has continued the warm spell, averaging more than 12 degrees above normal, including Monday’s unseasonable, 23-degree temperature surplus. Northwest winds gusting over 40 mph will sweep across the area Tuesday, bringing an influx of colder air. The core of this rare polar air is expected to settle across the area Wednesday and Thursday, with high temperatures in the 20s forecast. This cold snap is not associated with a major pattern change. By next week, forecasts suggest that mild air will return for an extended period.