Temperatures later this week are forecast to rise into the mid and upper 90s and will likely be the hottest weather we’ve felt in nearly 7 years, since the summer of 2012. An Excessive Heat Warning has been issued for Jo Daviess, Stephenson, Carroll, Whiteside, Lee, Ogle and DeKalb counties while a Heat Advisory has been issued for Green, Rock, Walworth, Winnebago, Boone and McHenry counties.
Isolated thunderstorms developed east of Rockford Wednesday afternoon along a lake breeze but have been mostly focused over southeast Wisconsin and northeast Illinois. To the west, a complex of thunderstorms over Iowa moved into Illinois with severe thunderstorms moving through west-central Illinois. The northern edge of this complex weakened quite a bit to only showers in northwest Illinois. Little relief from the warm and muggy air is expected Wednesday night.
Thunderstorms are forecast to develop over northern Iowa and southern Minnesota late Wednesday evening, moving east and southeast into Wisconsin. While most of the activity will remain in Wisconsin, more of a southward track is possible into southern Wisconsin and northern Illinois Thursday morning. If this complex of storms develops and moves into the Stateline it could delay how quickly temperatures warm during the afternoon. However, strong southwest winds are expected to develop during the afternoon and evening pushing temperatures into the low to mid 90s during the afternoon. Peak heat index values could be as high as 105 degrees during the late afternoon.
Friday is the biggest day of concern with little opportunity for rain or thunderstorms. Highs Friday afternoon will fall just shy of 100 degrees! The heat index Friday could peak as high as 115 degrees in some locations. The last time the high temperature was that high in Rockford was July 25th, 2012 when the mercury reached 99 degrees!
An approaching cold front will bring a chance for thunderstorms Saturday afternoon over Wisconsin and far northern Illinois, possibly tempering the heat some during the afternoon. The front will pass Sunday bringing temperatures back down into the 80s for the end of the weekend and next week.