OFallon Missouri Weather

OFallon - Weather Data from OFallon, MO

Latitude: N 38° 50' 20" Longitude: W 90° 43' 42" Altitude: 532 ft

CDT UTC Last station update CDT

WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com

Updated: Tuesday, 11-Aug-2026 04:00 pm

Tonight Thunder storm	Wednesday Thunder storm Hot!	Wednesday night Thunder storm	Thursday Thunder storm Hot!	Thursday night Partly Cloudy	Friday Partly Cloudy Hot!	Friday night Fog late	Saturday Sunny Hot!
<.1 in.	.1 in.	.1 in.	<.1 in.
Low: 77°	High: 92°	Low: 76°	High: 94°	Low: 76°	High: 96°	Low: 72°	High: 100°
	Heat: 103°		Heat: 107°		Heat: 106°		Heat: 109°
S 6-21 mph	W→SSW 6-21 mph	ESE→S 5-16 mph	S 5-22 mph	SE→SW 5-17 mph	ESE 4-22 mph	ESE 4-17 mph	SW 4-21 mph
	UV: 7 High		UV: 7 High		UV: 7 High		UV: 8 Very High

Tonight	Partly cloudy. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thunderstorms likely, some possibly severe. Low 77°. Wind south around 6 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Wednesday	Partly cloudy. Light to moderate fog in the morning. A chance of rain. Scattered thunderstorms likely. Hot. High 92°. Heat index up to 103°. UV index up to 7. Wind west around 6 mph, gusting to 21 mph, in the morning, becoming south-southwest in the afternoon. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Wednesday night	Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Moderate fog in the evening, then moderate to dense fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 76°. Wind east-southeast around 5 mph, gusting to 16 mph, in the evening, becoming south after midnight. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Thursday	Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain. Scattered thunderstorms likely. Hot. High 94°. Heat index up to 107°. UV index up to 7. Wind south around 5 mph, gusting to 22 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch.
Thursday night	Mostly clear in the evening, becoming partly cloudy after midnight. Low 76°. Wind southeast around 5 mph, gusting to 17 mph, in the evening, becoming southwest after midnight.
Friday	Partly cloudy. Very hot. High 96°. Heat index up to 106°. UV index up to 7. Wind east-southeast around 4 mph, gusting to 22 mph.
Friday night	Fair in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Low 72°. Wind east-southeast around 4 mph, gusting to 17 mph.
Saturday	Sunny. Very hot. High 100°. Heat index up to 109°. UV index up to 8. Wind southwest around 4 mph, gusting to 21 mph.
Saturday night	Clear. Low 73°. Wind south around 4 mph.
Sunday	Sunny in the morning, becoming partly to mostly sunny in the afternoon. Very hot. High 101°. Heat index up to 108°. UV index up to 9. Wind west-southwest around 7 mph, gusting to 24 mph.
Sunday night	Partly cloudy. Low 70°. Wind north around 5 mph, gusting to 16 mph.
Monday	Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Hot. High 92°. Heat index up to 96°. UV index up to 8. Wind north-northeast around 5 mph, gusting to 24 mph.
Monday night	Partly to mostly cloudy in the evening, becoming clear after midnight. Patchy light fog after midnight. Low 65°. Wind northeast around 6 mph, gusting to 20 mph, in the evening, becoming east after midnight.

WXSIM forecast formatting script by Saratoga-Weather.org.

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