St. Louis, Missouri – The morning sun is already baking pavement across the St. Louis metro, and the hottest part of the day hasn’t even arrived. Thick humidity is building over eastern Missouri and southwest Illinois, setting the stage for several days of dangerous summer heat that could affect everything from afternoon commutes to outdoor events.
According to the National Weather Service in St. Louis, a Heat Advisory begins at noon and remains in effect through 7 p.m. Tuesday for portions of eastern Missouri and southwest Illinois. Afternoon heat index values between 100 and 105 degrees are expected, creating conditions that can quickly lead to heat exhaustion or heat stroke without proper precautions.
Today’s high reaches 94 degrees under mostly sunny skies, with only a slight chance of an afternoon thunderstorm. The humidity will make it feel much hotter. Sunday brings another steamy day with highs near 91 degrees and heat index values again approaching 102 degrees, along with a 40 percent chance of afternoon thunderstorms.
The hottest stretch continues into early next week. Monday climbs back to 94 degrees under sunny skies, while Tuesday reaches 95 degrees before slightly cooler air arrives later in the week. The broader weather pattern favors persistent heat across the central United States as a strong upper-level ridge expands eastward. While isolated thunderstorms remain possible at times, organized severe weather and tornado potential around St. Louis appear low through Tuesday.
If you’re traveling on Interstates 44, 55, 64, 70, or 270, keep extra water in your vehicle and avoid unnecessary stops during peak afternoon heat. Construction crews, delivery drivers, gardeners, and anyone working outdoors should schedule frequent breaks in air-conditioned spaces. Never leave children or pets inside parked vehicles, even for a few minutes.
Warm nights, with lows mainly in the middle to upper 70s, will provide little overnight relief. That prolonged warmth allows heat stress to build over multiple days, especially for those without reliable cooling.
Long-range outlooks continue to support above-normal temperatures into late next week, meaning the summer heat will likely remain the dominant weather story across the St. Louis region.
How hot is it where you are today? Share your temperature or tell us how you’re staying cool across the metro.
Five-Day Forecast for St. Louis, Missouri
- Sunday: Mostly sunny, then chance of thunderstorms. High 91°F, Low 74°F.
- Monday: Sunny and hot. High 94°F, Low 78°F.
- Tuesday: Sunny and hot. High 95°F, Low 71°F.
- Wednesday: Sunny. High 86°F, Low 66°F.
- Thursday: Mostly sunny with a slight chance of showers. High 83°F, Low 68°F.
