Some hit-or-miss showers/t'showers are passing through now & will continue into tonight to Monday morning.
After a break with south-southwest to south winds at 15-25 mph with highs of 87-91 & heat indices near 97-102 with 70s dew points, severe risk will develop..............
5 p.m.-12 a.m. time frame seems good for any severe weather risk Monday night.
A lead supercell could pop & kick out of eastern Illinois & pass early in the evening (with wind, hail & isolated tornado threat), followed by the back-building line later in the evening.
Line will feature some embedded supercells, bows & LEWPs & perhaps even a developing Bookend Vortex, a.k.a. comma head on the northern part of the evolving line. This may all result in a wind damage risk, but also the risk for a couple of embedded tornadoes. Isolated large hail may occur in embedded supercells.
Heavy rainfall of near 1 to 3" is possible with a few isolated +3" amounts as storms will be torrential & may decelerate & train just a bit over the area.
With a north to northwest wind at 10-25 mph, it will still be humid Tuesday with dew points of 68-73 with 80s.
As a secondary cold from & a shortwave pass, some scattered showers & storms will be possible.
The humidity will drop nicely Wednesday with 78-84 with only a few isolated showers & storms with second & final shortwave pivoting through (after 58-64 in the morning & then lows of 53-58 Wednesday night).
Thursday looks dry & pleasant with low humidity, sunshine with some clouds & highs 78-84.
It still think a late-season August heat wave with low to mid 90s with heat indices in the 100s is possible. Exact timing is in question, but it is definitely a feature ahead.