WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 31-May-2026 05:00 am
 
Today

Thunder storm
Thunder storm
Tonight

Thunder storm
Thunder storm
Monday

Thunder storm
Thunder storm
Monday
night
Mostly Cloudy
Mostly Cloudy
Tuesday

Partly Cloudy
Partly Cloudy
Tuesday
night
Clear
Clear
Wednesday

Mostly Sunny
Mostly Sunny
Wednesday
night
Partly Cloudy
Partly Cloudy
<.1 in. .1 in. <.1 in.
High: 86° Low: 64° High: 85° Low: 64° High: 82° Low: 57° High: 82° Low: 57°
               
ESE
5-26
mph
ESE
3-21
mph
E
5-24
mph
NE
5-20
mph
NE
8-27
mph
E
5-23
mph
E
6-26
mph
ESE→SSE
4-22
mph
UV: 9
 Very High 
UV: 6
 High 
UV: 8
 Very High 
UV: 9
 Very High 

 

Today
 
Cloudy in the morning, becoming partly cloudy in the afternoon. A slight chance of rain. Scattered thunderstorms likely. Hot. High 86°. UV index up to 9. Wind east-southeast around 5 mph, gusting to 26 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Tonight
 
Fair to partly cloudy. Patchy light fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thunderstorms likely. Low 64°. Wind east-southeast around 3 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Monday
 
Partly cloudy in the morning, becoming mostly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. Scattered thunderstorms likely, some possibly severe. High 85°. UV index up to 6. Wind east around 5 mph, gusting to 24 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Monday night
 
Mostly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 64°. Wind northeast around 5 mph, gusting to 20 mph.
Tuesday
 
Partly cloudy in the morning, becoming sunny in the afternoon. High 82°. UV index up to 8. Wind northeast around 8 mph, gusting to 27 mph.
Tuesday night
 
Clear. Relatively cool. Low 57°. Wind east around 5 mph, gusting to 23 mph.
Wednesday
 
Mostly sunny in the morning, becoming sunny in the afternoon. High 82°. UV index up to 9. Wind east around 6 mph, gusting to 26 mph.
Wednesday night
 
Fair to partly cloudy in the evening, becoming fair after midnight. Relatively cool. Low 57°. Wind east-southeast around 4 mph, gusting to 22 mph, in the evening, becoming south-southeast after midnight.
Thursday
 
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Hot. High 86°. UV index up to 7. Wind south around 6 mph, gusting to 26 mph.
Thursday night
 
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Low 62°. Wind south around 6 mph, gusting to 21 mph.
Friday
 
Mostly cloudy in the morning, becoming cloudy in the afternoon. Rain likely. Scattered thunderstorms likely. High 81°. UV index up to 6. Wind south-southwest around 8 mph, gusting to 24 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Friday night
 
Dense overcast in the evening, becoming cloudy after midnight. Light to moderate fog. Rain likely. Scattered thunderstorms likely. Low 69°. Wind south around 6 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Saturday
 
Mostly cloudy in the morning, becoming cloudy in the afternoon. Moderate fog in the morning. Rain likely. Thunderstorms very likely, some possibly severe. High 82°. UV index up to 6. Wind southwest around 7 mph, gusting to 20 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Saturday night
 
Cloudy in the evening, becoming dense overcast after midnight. Light to moderate fog. A chance of rain in the evening, then rain likely after midnight. Thunderstorms very likely, some possibly severe. Low 72°. Wind south-southeast around 5 mph. Chance of precipitation 80 percent. Precipitation mostly around half an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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