WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Saturday, 25-Jul-2026 05:00 am
 
Today

Thunder storm
Thunder storm
Tonight

Thunder storm
Thunder storm
Sunday

Chance rain
Hot!
Chance rain
Hot!
Sunday
night
Fog late
Fog late
Monday

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

Mostly Sunny
Hot!
Mostly Sunny
Hot!
Tuesday
night
Partly Cloudy
Partly Cloudy
<.25 in. .1 in. <.1 in.
High: 88° Low: 73° High: 92° Low: 75° High: 95° Low: 74° High: 95° Low: 70°
Heat: 94°   Heat: 103°   Heat: 108°   Heat: 103°  
SW
6-23
mph
SW
2
mph
NW→SSW
3-20
mph
SSW
3
mph
SW
6-20→10-24
mph
W
6-18
mph
NW
8-26
mph
NE
4-21
mph
UV: 9
 Very High 
UV: 9
 Very High 
UV: 9
 Very High 
UV: 9
 Very High 

 

Today
 
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. A chance of rain. Scattered thundershowers possible. High 88°. Heat index up to 94°. UV index up to 9. Wind southwest around 6 mph, gusting to 23 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Tonight
 
Partly to mostly cloudy in the evening, becoming partly cloudy 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. Scattered thundershowers possible. Low 73°. Wind southwest around 2 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Sunday
 
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain. Hot. High 92°. Heat index up to 103°. UV index up to 9. Wind northwest around 3 mph, gusting to 20 mph, in the morning, becoming south-southwest in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Sunday night
 
Partly cloudy. Light to moderate fog after midnight. Low 75°. Wind south-southwest around 3 mph.
Monday
 
Partly to mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Hot. High 95°. Heat index up to 108°. UV index up to 9. Wind southwest around 6 mph, gusting to 20 mph, in the morning, becoming 10 mph, gusting to 24 mph, in the afternoon.
Monday night
 
Clear in the evening, becoming fair to partly cloudy after midnight. Low 74°. Wind west around 6 mph, gusting to 18 mph.
Tuesday
 
Partly to mostly sunny in the morning, becoming mostly sunny in the afternoon. Hot. High 95°. Heat index up to 103°. UV index up to 9. Wind northwest around 8 mph, gusting to 26 mph.
Tuesday night
 
Clear in the evening, becoming fair to partly cloudy after midnight. Low 70°. Wind northeast around 4 mph, gusting to 21 mph.
Wednesday
 
Partly cloudy. Hot. High 90°. Heat index up to 95°. UV index up to 7. Wind northeast around 2 mph, gusting to 22 mph, in the morning, becoming 6 mph, gusting to 23 mph, in the afternoon.
Wednesday night
 
Clear in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Low 68°. Wind northeast around 4 mph, gusting to 19 mph.
Thursday
 
Mostly sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. Hot. High 90°. Heat index up to 94°. UV index up to 8. Wind east-northeast around 5 mph, gusting to 23 mph.
Thursday night
 
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Relatively cool. Low 67°. Wind east around 4 mph, gusting to 21 mph.
Friday
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Hot. High 94°. UV index up to 9. Wind south around 4 mph, gusting to 23 mph, in the morning, becoming southeast around 7 mph, gusting to 23 mph, in the afternoon.
Friday night
 
Partly cloudy in the evening, becoming mostly cloudy after midnight. Low 71°. Wind southeast around 5 mph, gusting to 21 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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