The Illinois State Climatologist reports that 257 daily high temperature records have been set statewide this month. He worries that the early warmth could cause damage to agriculture as similar events did in 2007 and 2012:
A batch of crocus on the south side of our office building is a reminder of the impacts of warm weather in February. Both January and February have been mild. But on top of that has been a record-setting streak of 60s and 70s in the past week. As a result, many early season perennials such as crocus are coming out a little early. In the past, such warm weather has made any early vegetation vulnerable to the inevitable freeze later on. In 2007 and 2012, a similar scenario played out with damage to corn, winter wheat, alfalfa, and fruit crops across Illinois. The 2007 event was well documented in this report.
Meanwhile, a cold front pushed through last night with dog-frightening thunder, so it's now just above freezing in Chicago and promises to drop to about -5°C this weekend.