WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Thursday, 11-Jun-2026 05:00 am
 
Today

Thunder storm
Hot!
Thunder storm
Hot!
Tonight

Thunder storm
Thunder storm
Friday

Fog a.m.
Fog a.m.
Friday
night
Fog late
Fog late
Saturday

Thunder storm
Thunder storm
Saturday
night
Thunder storm
Thunder storm
Sunday

Mostly Sunny
Mostly Sunny
Sunday
night
Partly Cloudy
Partly Cloudy
<.1 in. <.25 in. .1 in. <.1 in.
High: 93° Low: 68° High: 85° Low: 66° High: 85° Low: 70° High: 78° Low: 61°
Heat: 100°              
S
9-29→15-31
mph
W
10-24→4-16
mph
WNW
5-24
mph
E→SSE
3-19
mph
S
8-25
mph
SSW→WNW
7-24
mph
NW
10-28
mph
NW
4-25
mph
UV: 9
 Very High 
UV: 10
 Very High 
UV: 6
 High 
UV: 9
 Very High 

 

Today
 
Partly to mostly sunny in the morning, becoming mostly sunny 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 93°. Heat index up to 100°. UV index up to 9. Wind south around 9 mph, gusting to 29 mph, in the morning, becoming 15 mph, gusting to 31 mph, in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Tonight
 
Partly cloudy in the evening, becoming clear after midnight. Patchy light fog. A chance of rain in the evening, then a slight chance of rain after midnight. Thunderstorms very likely, some possibly severe. Low 68°. Wind west around 10 mph, gusting to 24 mph, in the evening, becoming 4 mph, gusting to 16 mph, after midnight. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Friday
 
Sunny. Patchy light fog in the morning. High 85°. UV index up to 10. Wind west-northwest around 5 mph, gusting to 24 mph.
Friday night
 
Mostly clear in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Low 66°. Wind east around 3 mph, gusting to 19 mph, in the evening, becoming south-southeast after midnight.
Saturday
 
Mostly cloudy to cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. Thunderstorms very likely, some severe. High 85°. UV index up to 6. Wind south around 8 mph, gusting to 25 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Saturday night
 
Partly to mostly cloudy in the evening, becoming cloudy after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Thunderstorms very likely, some severe. Low 70°. Wind south-southwest around 7 mph, gusting to 24 mph, in the evening, becoming west-northwest after midnight. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch.
Sunday
 
Partly to mostly sunny. High 78°. UV index up to 9. Wind northwest around 10 mph, gusting to 28 mph.
Sunday night
 
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Relatively cool. Low 61°. Wind northwest around 4 mph, gusting to 25 mph.
Monday
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. High 82°. UV index up to 8. Wind west-northwest around 6 mph, gusting to 25 mph.
Monday night
 
Partly cloudy in the evening, becoming fair after midnight. Relatively cool. Low 60°. Wind west-northwest around 4 mph, gusting to 21 mph.
Tuesday
 
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. High 85°. UV index up to 8. Wind southwest around 4 mph, gusting to 24 mph, in the morning, becoming 8 mph, gusting to 25 mph, in the afternoon.
Tuesday night
 
Partly cloudy in the evening, becoming fair after midnight. Relatively cool. Low 62°. Wind southwest around 5 mph, gusting to 23 mph.
Wednesday
 
Sunny. Hot. High 87°. UV index up to 10. Wind southwest around 6 mph, gusting to 27 mph, in the morning, becoming 10 mph, gusting to 27 mph, in the afternoon.
Wednesday night
 
Clear. Breezy. Low 64°. Wind south-southwest around 10 mph, gusting to 25 mph, in the evening, becoming 13 mph, gusting to 22 mph, after midnight.

WXSIM forecast formatting script by Saratoga-Weather.org.

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