WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 10-May-2026 04:00 pm
 
Tonight

Partly Cloudy
Partly Cloudy
Monday

Sunny
Sunny
Monday
night
Mostly Clear
Mostly Clear
Tuesday

Mostly Sunny
Mostly Sunny
Tuesday
night
Chance rain
Chance rain
Wednesday

Fog a.m.
Fog a.m.
Wednesday
night
Clear
Clear
Thursday

Sunny
Sunny
.25 in.
Low: 48° High: 75° Low: 49° High: 80° Low: 55° High: 75° Low: 50° High: 77°
               
NNW→SSW
2-17
mph
W
5-23
mph
SW
4-19
mph
SW
9-28
mph
W
7-21
mph
WNW
9-27
mph
NNW→ENE
4-24
mph
SE
5-24
mph
UV: 7
 High 
UV: 7
 High 
UV: 7
 High 
UV: 8
 Very High 

 

Tonight
 
Partly cloudy in the evening, becoming clear after midnight. Cool. Low 48°. Wind north-northwest around 2 mph, gusting to 17 mph, in the evening, becoming south-southwest after midnight.
Monday
 
Sunny. High 75°. UV index up to 7. Wind west around 5 mph, gusting to 23 mph.
Monday night
 
Mostly clear. Cool. Low 49°. Wind southwest around 4 mph, gusting to 19 mph.
Tuesday
 
Sunny in the morning, becoming mostly sunny in the afternoon. High 80°. UV index up to 7. Wind southwest around 9 mph, gusting to 28 mph.
Tuesday night
 
Partly cloudy in the evening, becoming mostly clear after midnight. 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. Precipitation showery or intermittent. Low 55°. Wind west around 7 mph, gusting to 21 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Wednesday
 
Sunny. Patchy light fog in the morning. High 75°. UV index up to 7. Wind west-northwest around 9 mph, gusting to 27 mph.
Wednesday night
 
Clear. Cool. Low 50°. Wind north-northwest around 4 mph, gusting to 24 mph, in the evening, becoming east-northeast after midnight.
Thursday
 
Sunny. High 77°. UV index up to 8. Wind southeast around 5 mph, gusting to 24 mph.
Thursday night
 
Partly cloudy in the evening, becoming mostly cloudy after midnight. A slight chance of rain after midnight. Cool. Low 52°. Wind southeast around 9 mph, gusting to 22 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Friday
 
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. A slight chance of rain. Scattered thundershowers possible. Breezy and hot. High 86°. UV index up to 7. Wind south around 14 mph, gusting to 32 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Friday night
 
Fair in the evening, becoming clear after midnight. Breezy. Low 60°. Wind south around 12 mph, gusting to 28 mph.
Saturday
 
Partly to mostly sunny in the morning, becoming cloudy in the afternoon. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely, some possibly severe. Breezy and hot. High 87°. UV index up to 7. Wind south around 12 mph, gusting to 29 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. Rain very likely. Severe thunderstorms likely, with possible tornados. Breezy and warm. Low 69°. Wind south-southwest around 11 mph, gusting to 23 mph. Chance of precipitation 80 percent. Precipitation mostly around an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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