St. Louis woke up Monday, July 20, 2026, to a murky mix of patchy fog and pockets of smoke that cut visibility in spots across the metro. Early readings hovered around 72°F with thick, sticky humidity. That soupy start is on track to turn into a hot, uncomfortable afternoon away from the riverfront.
Afternoon Heat And Heat Advisory
Highs Monday, July 20, are expected to top out near 94°F, with heat-index values climbing into the low 100s. The National Weather Service has a Heat Advisory in effect through 7 p.m. CDT Tuesday, July 21, calling for heat-index readings up to roughly 108°F. Southeast winds stay on the light side today, while a breezier west wind on Tuesday could make the already brutal heat feel even more oppressive.
Fog, Smoke And Storm Chances
Through late morning, expect patchy fog and patchy smoke to hang around, at times knocking visibility down to a quarter-mile in localized areas and taking a toll on air quality. A line of showers and a chance of thunderstorms may brush the northern suburbs late tonight into Tuesday morning, mainly along and north of I-70. Any storms that sneak in could drop heavy rain and produce isolated strong wind gusts.
Where To Find Relief
Cooling centers and partner agencies around the region are open with air conditioning and water for those who need a break from the heat. A current roster of locations, hours, and addresses is available from Heat Up St. Louis. If you do not have air conditioning, call 2-1-1 or the nonprofit hotline at 314-241-0001 for help finding assistance and shelter.
Looking Ahead
A much cooler and drier airmass is expected to move in on Wednesday, July 22, dropping highs into the mid-80s for a few days before temperatures trend back up later in the week, according to the National Weather Service. Until the advisory expires, take frequent breaks if you need to be outside, drink plenty of water, and check in on elderly neighbors and anyone without reliable cooling.
