The last weekend of summer definitely felt like it as the high temperature in Rockford reached 93 degrees Sunday. This tied the previous record high of 93 degrees for the 19th of September most recently set back in 1948 (although not really that recently), as well as in 1947 and 1925. Sunday’s high temperature wrapped up a very unseasonably warm weekend, but likely the last upper 80/low 90 degree high temperatures we’ll feel (hopefully) this year. A strong cold front coming in Monday night will bring temperatures back to, and slightly below, where they should be for late September.
Cloud cover will continue to increase Sunday evening as low pressure lifts north from the Gulf. This low has a little more Gulf moisture associated with it, bringing in a slight chance for a few light showers Monday morning. As that low moves over the Great Lakes late morning, drier air will briefly move in for Monday afternoon. Temperatures may not be quite as hot as Sunday, but the humidity will be a little higher thanks to increasing dew point temperatures. Highs on Monday will warm into the low 80s – still above average.
A strong trough (dip in the jet stream) will continue to move east across the Plains and Midwest during the day Monday. This will help pull a cold front closer to the area during the afternoon and evening. A redevelopment of showers and thunderstorms are possible towards late evening, but likely more-so during the overnight. Some of those storms could be strong with gusty winds and heavy rainfall. A drop in temperatures is then expected for Tuesday, falling even further Tuesday night and Wednesday. Wednesday marks the official start to Fall, and right now the forecast high for the afternoon is currently 68 degrees! Overnight lows Wednesday night will drop into the low to mid 40s. Temperatures throughout the remainder of the week will remain in the 60s and 70s, coming back close to 80 degrees both Friday and Sunday.