Temperatures Wednesday were the warmest they’ve been all week, rising to 88 degrees in Rockford. But the heat index for some pushed well into the 90s, especially to the south, where dew point temperatures were the highest.
A lake breeze moving inland through Chicago produced quite a few thunderstorms early Wednesday afternoon. Locally, we had a few very isolated showers and thunderstorms develop along a weak surface trough (boundary) over northern Illinois. Weak winds in the atmosphere did not allow those showers and storms to move, causing them to remain fairly stationary for a time during the late afternoon and evening. Radar estimates north of Byron and Rockford, right around Loves Park, received anywhere from one to two inches. Elsewhere it remained bone dry.
Widely isolated showers will continue through the early overnight as the weak surface boundary remains in place. This will also keep a little cloud cover around for some through the night. Where the skies are clear fog is likely to develop by early Thursday morning. Temperatures Wednesday night will fall into the mid 60s. Isolated showers and thunderstorms are possible once again Thursday, but some of the forcing that was present on Wednesday will be much lighter for Thursday afternoon. Highs on Thursday will warm near 90 degrees.