Showers and thunderstorms will move across parts of the area overnight into early Monday morning. With the return of extremely humid conditions, heavy rainfall is possible from some of the thunderstorms. Flash flooding could become a problem and the National Weather Service has issued a flash flood watch for much of the area.
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The rain may impact your Monday morning commute.
Additional thunderstorms are possible later Monday and Monday night, especially north into portions of central Illinois where a moderate risk of severe storms exists.
By late morning Monday, the heat really builds in across the region as the sky brightens. Once any storms move away, a blistering afternoon is expected with temperatures climbing into the middle 90s. Dew point temperatures are expected to be quite high in the middle to upper 70s. That combination will create dangerous heat index values above 105°.
The National Weather Service has issued a heat advisory for much of the area including all of metro St. Louis for Monday afternoon and evening.
Extreme heat like what is expected Monday can quickly cause heat exhaustion or heat stroke if precautions are not taken. The very young, the elderly, those without air conditioning and those participating in strenuous outdoor activities will be the most susceptible.
Drinking plenty of water, staying out of the sun and spending time in air conditioning are important during this time. Check on your neighbors and remember your pets need relief from the heat as well.