Sunday was the hottest day of 2020 via the heat index. It peaked at 100-111 viewing area-wide (most observation sites were 101-106). The highest heat indices of 108-111 seemed to be in a strip from Edgar County, Illinois, through western Fountain, Benton to southwestern Newton counties then Livingston to Kankakee counties, then up towards the Chicago area.
It was also one of the hottest days of 2020 for the actual air temperature with highs 90-96.
At our WLFI ob site, we hit 95 with a peak heat index of 107. The Purdue Airport hit 95 with a heat index peaking at 105.
For the actual air temperature, Chicago officially hit 96, Kenosha, Wisconsin shot up to 96, while Benton Harbor, Michigan reached 95. Milwaukee hit 95 with a morning low of 75. Even way up in northern Michigan, Traverse City saw a high of 92 with a heat index of 102.
Overnight was oppressive in our area, as well, with lows of 72-78.
Scattered storms are possible this afternoon along the actual cold front & with apparent MCV, followed by some scattered showers & storms behind the cold front in the north & northwest wind.
A couple isolated severe storms are possible with the front & MCV despite paltry bulk shear values. If they were higher, there would be a much more robust severe weather risk. Often MCV locally-enhance the shear & wind fields. This subtle one isn't doing it quite as much as the others have.
Locally-heavy rainfall is also possible.
After highs in the 80s to lower 90s with heat indices in the 90s to lower 100s, temperatures will fall this afternoon to 70s to 80s with the frontal passage, clouds & rainfall.
Patchy fog is possible tonight after 4 a.m. (as northwest wind decreases to 2-4 mph) as any scattered rainfall departs. Lows will run in the 60-64 range.
Tuesday looks a bit cooler & less humid with highs 84-90 with heat indices dropping to 86-92 with 60s dew points. There will be a west to west-northwest breeze at 8-14 mph.
Certainly not a crisp, comfy, cool day & you will sweat, but it will be better.
Problem with Wednesday is that high dew points will pool ahead of a cold front in the afternoon to evening at 69-74, especially in our northwestern counties.
Humidity may be held in check part of the day with 62-67 dew points, but it will get muggy by afternoon-evening.
With highs 86-90, it will feel like 90-96 with a southwest wind at 10-20 mph.
You can see the cold front north of the area Tuesday evening with a few spotty showers & t'showers:
The remnant circulation of Tropical Storm Hanna will approach Wednesday night from Texas, Oklahoma & Kansas:
Showers & storms are possible Thursday to Friday with front stalling over the area & low pressure (remnant circulation of Hanna) riding front.
Exact position or track of the low & front will determine where the axis of heavier rainfall occurs.
Kept 20% POPs for Saturday behind front as weak shortwave pivots through.
Nice cool-down should follow with lower humidity & highs 78-84 with lows 55-60 by Sunday. Hotter, humid weather returns with time next week as hot upper ridge in the West migrates eastward.