WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Tuesday, 26-May-2026 05:00 am
 
Today

Mostly Cloudy
Mostly Cloudy
Tonight

Fog late
Fog late
Wednesday

Partly Cloudy
Partly Cloudy
Wednesday
night
Fog late
Fog late
Thursday

Partly Cloudy
Partly Cloudy
Thursday
night
Fog late
Fog late
Friday

Fog a.m.
Fog a.m.
Friday
night
Partly Cloudy
Partly Cloudy
<.1 in.
High: 81° Low: 61° High: 85° Low: 59° High: 84° Low: 59° High: 82° Low: 57°
               
ENE
4-24
mph
NE
3-20
mph
N
3-23
mph
NNE
2-19
mph
NE
5-23
mph
NE
5-16
mph
E
7-24
mph
E
4-22
mph
UV: 6
 High 
UV: 8
 Very High 
UV: 8
 Very High 
UV: 7
 High 

 

Today
 
Mostly cloudy. High 81°. UV index up to 6. Wind east-northeast around 4 mph, gusting to 24 mph.
Tonight
 
Partly cloudy. Patchy light fog after midnight. Low 61°. Wind northeast around 3 mph, gusting to 20 mph.
Wednesday
 
Partly cloudy in the morning, becoming sunny in the afternoon. Warm. High 85°. UV index up to 8. Wind north around 3 mph, gusting to 23 mph.
Wednesday night
 
Mostly clear in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Low 59°. Wind north-northeast around 2 mph, gusting to 19 mph.
Thursday
 
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. A slight chance of rain in the afternoon. High 84°. UV index up to 8. Wind northeast around 5 mph, gusting to 23 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Thursday night
 
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Low 59°. Wind northeast around 5 mph, gusting to 16 mph.
Friday
 
Partly to mostly cloudy in the morning, becoming mostly cloudy in the afternoon. Patchy light fog in the morning. High 82°. UV index up to 7. Wind east around 7 mph, gusting to 24 mph.
Friday night
 
Fair to partly cloudy in the evening, becoming fair after midnight. Relatively cool. Low 57°. Wind east around 4 mph, gusting to 22 mph.
Saturday
 
Partly 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 80°. UV index up to 8. Wind east-northeast around 5 mph, gusting to 26 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Saturday night
 
Partly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Low 61°. Wind north-northeast around 6 mph, gusting to 17 mph, in the evening, becoming east after midnight.
Sunday
 
Mostly cloudy to cloudy. High 77°. UV index up to 5. Wind east around 6 mph, gusting to 22 mph.
Sunday night
 
Partly cloudy in the evening, becoming clear after midnight. Relatively cool. Low 57°. Wind east around 4 mph, gusting to 19 mph.
Monday
 
Sunny. High 81°. UV index up to 10. Wind east around 4 mph, gusting to 25 mph.
Monday night
 
Clear. Relatively cool. Low 56°. Wind east around 2 mph, gusting to 20 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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