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

Thunder storm
Thunder storm
Saturday

Thunder storm
Thunder storm
Saturday
night
Thunder storm
Thunder storm
Sunday

Rain likely
Rain likely
Sunday
night
Fog late
Fog late
Monday

Fog a.m.
Fog a.m.
Monday
night
Partly Cloudy
Partly Cloudy
Tuesday

Chance rain
Chance rain
.35 in. .75 in. .25 in. <.1 in. <.1 in.
Low: 74° High: 80° Low: 72° High: 84° Low: 68° High: 87° Low: 68° High: 86°
               
NNW→S
2-17
mph
ESE→NNE
3-18
mph
NNE
5-17
mph
NNE
8-26
mph
NNE
6-24
mph
NNE
7-25
mph
NNE
5-23
mph
NE
6-24
mph
UV: 5
 Medium 
UV: 9
 Very High 
UV: 9
 Very High 
UV: 9
 Very High 

 

Tonight
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Moderate fog. Rain very likely. Scattered thunderstorms likely. Low 74°. Wind north-northwest around 2 mph, gusting to 17 mph, in the evening, becoming south after midnight. Chance of precipitation 80 percent. Precipitation mostly between a quarter and half an inch.
Saturday
 
Mostly cloudy to cloudy in the morning, becoming cloudy in the afternoon. Light to moderate fog. Rain. Scattered thunderstorms likely. High 80°. UV index up to 5. Wind east-southeast around 3 mph, gusting to 18 mph, in the morning, becoming north-northeast in the afternoon. Chance of precipitation near 100 percent. Precipitation mostly between half an inch and one inch.
Saturday night
 
Mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Moderate fog in the evening, then light to moderate fog after midnight. Rain likely in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Low 72°. Wind north-northeast around 5 mph, gusting to 17 mph. Chance of precipitation 70 percent. Precipitation mostly around a quarter of an inch.
Sunday
 
Mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Rain likely. High 84°. UV index up to 9. Wind north-northeast around 8 mph, gusting to 26 mph. Chance of precipitation 60 percent. Precipitation mostly less than a tenth of an inch.
Sunday night
 
Clear. Patchy light fog in the evening, then light to moderate fog after midnight. Low 68°. Wind north-northeast around 6 mph, gusting to 24 mph.
Monday
 
Sunny. Light to moderate fog in the morning. High 87°. UV index up to 9. Wind north-northeast around 7 mph, gusting to 25 mph.
Monday night
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 68°. Wind north-northeast around 5 mph, gusting to 23 mph.
Tuesday
 
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. A slight chance of rain in the morning, then a chance of rain in the afternoon. High 86°. UV index up to 9. Wind northeast around 6 mph, gusting to 24 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch.
Tuesday night
 
Fair. Patchy light fog in the evening, then light to moderate fog after midnight. Low 71°. Wind east-northeast around 4 mph, gusting to 20 mph.
Wednesday
 
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain. Precipitation showery or intermittent. High 87°. Heat index up to 94°. UV index up to 6. Wind east-southeast around 4 mph, gusting to 20 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch.
Wednesday night
 
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog. Low 73°. Wind southeast around 2 mph, gusting to 17 mph, in the evening, becoming south-southwest after midnight.
Thursday
 
Partly cloudy. Patchy light fog in the morning. A chance of rain. High 90°. Heat index up to 98°. UV index up to 8. Wind west around 5 mph, gusting to 21 mph, in the morning, becoming 9 mph, gusting to 25 mph, in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Thursday night
 
Partly to mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 72°. Wind west around 4 mph, gusting to 21 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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