WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Thursday, 19-Mar-2026 05:00 am
 
Today

Mostly Cloudy
Mostly Cloudy
Tonight

Partly Cloudy
Partly Cloudy
Friday

Mostly Sunny
Mostly Sunny
Friday
night
Fog late
Fog late
Saturday

Fog a.m.
Fog a.m.
Saturday
night
Clear
Clear
Sunday

Mostly Sunny
Mostly Sunny
Sunday
night
Mostly Clear
Mostly Clear
High: 77° Low: 46° High: 84° Low: 45° High: 80° Low: 51° High: 79° Low: 37°
               
SW
3-23
mph
SW
2
mph
WSW
5-18→9-26
mph
NW→NE
3-19
mph
ESE→S
3-21
mph
S
5→8
mph
SW→NW
9-23→13-29
mph
N
11-28
mph
UV: 5
 Medium 
UV: 6
 High 
UV: 6
 High 
UV: 6
 High 

 

Today
 
Partly to mostly cloudy in the morning, becoming mostly sunny in the afternoon. Unusually warm. High 77°. UV index up to 5. Wind southwest around 3 mph, gusting to 23 mph.
Tonight
 
Fair in the evening, becoming fair to partly cloudy after midnight. Low 46°. Wind southwest around 2 mph.
Friday
 
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Exceptionally hot. High 84°. UV index up to 6. Wind west-southwest around 5 mph, gusting to 18 mph, in the morning, becoming 9 mph, gusting to 26 mph, in the afternoon.
Friday night
 
Partly cloudy in the evening, becoming fair after midnight. Patchy light fog after midnight. Low 45°. Wind northwest around 3 mph, gusting to 19 mph, in the evening, becoming northeast after midnight.
Saturday
 
Sunny. Patchy light fog in the morning. Unusually warm. High 80°. UV index up to 6. Wind east-southeast around 3 mph, gusting to 21 mph, in the morning, becoming south in the afternoon.
Saturday night
 
Clear in the evening, becoming fair after midnight. Low 51°. Wind south around 5 mph in the evening, becoming 8 mph after midnight.
Sunday
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Unusually warm. High 79°. UV index up to 6. Wind southwest around 9 mph, gusting to 23 mph, in the morning, becoming northwest around 13 mph, gusting to 29 mph, in the afternoon.
Sunday night
 
Clear in the evening, becoming mostly clear after midnight. Breezy. Low 37°. Wind north around 11 mph, gusting to 28 mph.
Monday
 
Sunny. High 60°. UV index up to 5. Wind north-northeast around 7 mph, gusting to 26 mph.
Monday night
 
Mostly clear in the evening, becoming partly cloudy after midnight. Low 37°. Wind east around 5 mph, gusting to 21 mph.
Tuesday
 
Partly cloudy. Mild. High 67°. UV index up to 5. Wind southeast around 7 mph, gusting to 24 mph.
Tuesday night
 
Mostly cloudy in the evening, becoming cloudy after midnight. Low 47°. Wind southeast around 6 mph, gusting to 22 mph.
Wednesday
 
Mostly cloudy to cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Unusually warm. High 79°. UV index up to 5. Wind south around 7 mph, gusting to 17 mph, in the morning, becoming 10 mph, gusting to 26 mph, in the afternoon.
Wednesday night
 
Clear. Breezy. Low 52°. Wind south around 12 mph, gusting to 22 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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