St. Louis/ Weather & Environment

Foggy St. Louis Morning To Sizzle In 90-Degree Weekend Heat

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Published on September 11, 2026
Foggy St. Louis Morning To Sizzle In 90-Degree Weekend HeatSource: Unsplash/ Will

St. Louis is waking up to fog and mist Friday before a warm, increasingly summery stretch takes over. The city is forecast to reach 84 degrees under mostly cloudy skies, with temperatures climbing into the low 90s by Saturday and staying there into next week.

Fog Fades By Midmorning

Early conditions are foggy, with temperatures near 66 degrees and visibility reduced in spots. Patchy fog should improve by 10 a.m., but drivers heading across the region may still encounter pockets of thicker fog, especially near river valleys and outside the urban core.

A Dense Fog Advisory remains in effect through 10 a.m. for parts of central and northeast Missouri and west-central Illinois, according to the National Weather Service St. Louis. Once the fog lifts, light east to southeast winds and mostly cloudy skies will carry the area through the afternoon, with only a small chance of a passing shower.

Weekend Heat Builds Quickly

Friday night will stay mostly cloudy with a low around 70. Saturday brings mostly sunny skies and a high near 91, while Sunday will be similarly warm with a slight chance of rain showers after 1 p.m.

The warmup continues Monday with sunshine and a high near 92, followed by a hotter Tuesday and Wednesday near 93 degrees. Shower and thunderstorm chances increase from Tuesday afternoon into Thursday, when rain chances reach about 50% and the high remains near 91.

Outdoor Plans May Need Extra Water

For Friday, the main nuisance is reduced visibility early in the day, followed by increasing heat over the weekend. Anyone planning outdoor activities should account for the jump from the 80s into the 90s and keep an eye on the forecast as storm chances become more noticeable next week.