WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Wednesday, 18-Mar-2026 05:00 am
 
Today

Mostly Sunny
Mostly Sunny
Tonight

Partly Cloudy
Partly Cloudy
Thursday

Partly Cloudy
Partly Cloudy
Thursday
night
Partly Cloudy
Partly Cloudy
Friday

Sunny
Sunny
Friday
night
Partly Cloudy
Partly Cloudy
Saturday

Sunny
Sunny
Saturday
night
Clear
Clear
High: 64° Low: 42° High: 74° Low: 42° High: 79° Low: 46° High: 82° Low: 48°
               
SSE→WSW
7-28
mph
SSW
2-18
mph
WSW→E
3-21
mph
ENE→WSW
calm

W
3-18→8-24
mph
W
6-17→2
mph
WSW
3-22
mph
SSW
4→7
mph
UV: 4
 Medium 
UV: 5
 Medium 
UV: 6
 High 
UV: 6
 High 

 

Today
 
Partly to mostly sunny. Mild. High 64°. UV index up to 4. Wind south-southeast around 7 mph, gusting to 28 mph, in the morning, becoming west-southwest in the afternoon.
Tonight
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 42°. Wind south-southwest around 2 mph, gusting to 18 mph.
Thursday
 
Partly cloudy in the morning, becoming mostly sunny in the afternoon. Unusually warm. High 74°. UV index up to 5. Wind west-southwest around 3 mph, gusting to 21 mph, in the morning, becoming east in the afternoon.
Thursday night
 
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Low 42°. Wind east-northeast near calm in the evening, becoming west-southwest after midnight.
Friday
 
Sunny. Unusually warm. High 79°. UV index up to 6. Wind west around 3 mph, gusting to 18 mph, in the morning, becoming 8 mph, gusting to 24 mph, in the afternoon.
Friday night
 
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Low 46°. Wind west around 6 mph, gusting to 17 mph, in the evening, becoming 2 mph after midnight.
Saturday
 
Sunny. Unusually hot. High 82°. UV index up to 6. Wind west-southwest around 3 mph, gusting to 22 mph.
Saturday night
 
Clear. Low 48°. Wind south-southwest around 4 mph in the evening, becoming 7 mph after midnight.
Sunday
 
Sunny in the morning, becoming partly to mostly cloudy in the afternoon. Unusually warm. High 79°. UV index up to 5. Wind south-southwest around 6 mph, gusting to 22 mph, in the morning, becoming north around 11 mph, gusting to 28 mph, in the afternoon.
Sunday night
 
Partly to mostly cloudy in the evening, becoming fair after midnight. A slight chance of rain. Low 39°. Wind north around 11 mph, gusting to 27 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Monday
 
Mostly sunny in the morning, becoming sunny in the afternoon. High 61°. UV index up to 6. Wind north around 8 mph, gusting to 27 mph.
Monday night
 
Fair to partly cloudy in the evening, becoming mostly cloudy after midnight. Low 39°. Wind north-northeast around 5 mph, gusting to 21 mph, in the evening, becoming east-northeast after midnight.
Tuesday
 
Cloudy. High 53°. Wind east-southeast around 9 mph, gusting to 26 mph.
Tuesday night
 
Cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Low 42°. Wind east-southeast around 7 mph, gusting to 24 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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