High temperatures Tuesday afternoon warmed into the low 90s in northern Illinois and southern Wisconsin, officially reaching 93 degrees in Rockford. This was our first 90 degree temperature in Rockford this year, and first 90 degree temperature since early August of last year.
Strong southerly winds combined with a ridge of high pressure allowed temperatures to warm nearly 20 degrees higher than what they were over the weekend. Dew points in the mid 60s pushed the heat index into the mid 90s in some spots. Highs Wednesday will rise back into the mid 80s, not quite as hot as Tuesday afternoon but still about 10 degrees above average.
Temperatures Tuesday evening are still rather mild, but have cooled quite a bit following an outflow boundary moving through northern Illinois and thunderstorms to the north. Winds shifting to the north following the outflow boundary (rain cooled air) will briefly bring temperatures into the upper 60s and low 70s in southern Wisconsin and northern Illinois. Overnight lows will dip into the upper 60s starting Wednesday. Thunderstorms will be possible Wednesday morning with the arrival of a cold front, with a severe threat in central Illinois.