Triple-digit heat indices likely across northern Illinois Wednesday

A compact low pressure system, known as an M.C.V - mesoscale convective vortex - is swinging into southwest Wisconsin this morning. While most of the activity has remained to our northwest, we are seeing a few spotty showers and thunderstorms develop across northwest Illinois. Expect any chance for rain to come to a close before mid-morning. 

 

Our attention will then turn to today's heat. A Heat Advisory will be in place for all of northern Illinois and southern Wisconsin beginning at 10AM this morning. The portion that includes Winnebago, Boone, McHenry, Ogle, and Lee County will run until 10 PM. Stephenson, Carroll, Jo-Daviess, and Whiteside County will be under the advisory until 7PM. And finally, the portion that includes southern Wisconsin will run until 8PM.

High temperatures this afternoon will soar into the low 90s. That, combined with dew point temperatures in the mid to upper 70s (gross) will allow heat indices to climb above 100°, likely ending as high as 105°-108°. Heat safety, heat safety, heat safety! Make sure you are making that a priority this afternoon as well as passing the same safety to your loved ones, your pets, and to those who may not have a reliable source of air conditioning. 

Some relief arrives in the form of a cold front during the late stages of Thursday. This will bring afternoon highs down into the mid to upper 80s for Friday and for the start of the weekend. However, with the heat dome to our south expanding back into the central plains, we can expect highs to climb back into the low 90s for Sunday and Monday.