WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Thursday, 12-Mar-2026 05:00 am
 
Today

Mostly Sunny
Mostly Sunny
Tonight

Partly Cloudy
Partly Cloudy
Friday

Partly Cloudy
Partly Cloudy
Friday
night
Partly Cloudy
Partly Cloudy
Saturday

Partly Cloudy
Partly Cloudy
Saturday
night
Mostly Cloudy
Mostly Cloudy
Sunday

Thunder storm
Thunder storm
Sunday
night
Thunder storm
Thunder storm
.5 in. .75 in.
.25 in.
High: 54° Low: 40° High: 60° Low: 36° High: 64° Low: 48° High: 64° Low: 27°
              WCh: 19°
WNW→SW
5-23→8-24
mph
SW
11-23→15-23
mph
WNW
13-28→10-29
mph
NW→ENE
4-22
mph
E
9-27
mph
ESE→SSE
8-23
mph
SSE→SSW
13-28
mph
WNW
18-35
mph
UV: 4
 Medium 

 

Today
 
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. High 54°. Wind west-northwest around 5 mph, gusting to 23 mph, in the morning, becoming southwest around 8 mph, gusting to 24 mph, in the afternoon.
Tonight
 
Partly cloudy. Breezy. Low 40°. Wind southwest around 11 mph, gusting to 23 mph, in the evening, becoming 15 mph, gusting to 23 mph, after midnight.
Friday
 
Partly cloudy. Breezy. High 60°. Wind west-northwest around 13 mph, gusting to 28 mph, in the morning, becoming 10 mph, gusting to 29 mph, in the afternoon.
Friday night
 
Partly to mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Low 36°. Wind northwest around 4 mph, gusting to 22 mph, in the evening, becoming east-northeast after midnight.
Saturday
 
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Mild. High 64°. UV index up to 4. Wind east around 9 mph, gusting to 27 mph.
Saturday night
 
Partly to mostly cloudy in the evening, becoming mostly cloudy after midnight. Low 48°. Wind east-southeast around 8 mph, gusting to 23 mph, in the evening, becoming south-southeast after midnight.
Sunday
 
Mostly cloudy to cloudy in the morning, becoming dense overcast in the afternoon. A chance of rain in the morning, then rain likely in the afternoon. Scattered thunderstorms likely. Breezy and mild. High 64°. Wind south-southeast around 13 mph, gusting to 28 mph, in the morning, becoming south-southwest in the afternoon. Chance of precipitation 80 percent. Precipitation mostly around half an inch.
Sunday night
 
Cloudy in the evening, becoming dense overcast after midnight. Rain likely in the evening, then a mix of snow and rain likely after midnight. Scattered thundershowers possible. Windy and cold. Low 27°. Wind chill ranging from 19 to 53. Wind west-northwest around 18 mph, gusting to 35 mph. Chance of precipitation 80 percent. Precipitation (liquid equivalent) mostly between half an inch and one inch. Snow accumulation about a quarter inch.
Monday
 
Dense overcast in the morning, becoming partly to mostly cloudy in the afternoon. A chance of snow in the morning, then a slight chance of snow in the afternoon. Windy and very cold. High 29°, but temperatures falling in the afternoon. Wind chill ranging from 10 to 18. Wind west-northwest around 17 mph, gusting to 34 mph. Chance of precipitation 30 percent. Precipitation (liquid equivalent) mostly less than a tenth of an inch. No snow accumulation expected.
Monday night
 
Clear. Very cold. Low 19°. Wind chill as low as 9. Wind west-northwest around 11 mph, gusting to 26 mph, in the evening, becoming 8 mph, gusting to 21 mph, after midnight.
Tuesday
 
Partly cloudy. High 39°. Wind west-northwest around 4 mph, gusting to 23 mph.
Tuesday night
 
Cloudy in the evening, becoming dense overcast after midnight. Snow likely. Cold. Low 30°. Wind chill ranging from 21 to 37. Wind east-southeast around 5 mph, gusting to 24 mph, in the evening, becoming 11 mph, gusting to 25 mph, after midnight. Chance of precipitation 60 percent. Precipitation (liquid equivalent) mostly less than a quarter of an inch. Snow accumulation about half an inch.
Wednesday
 
Mostly cloudy to cloudy in the morning, becoming cloudy in the afternoon. A slight chance of snow in the morning, then a slight chance of rain in the afternoon. High 44°. Wind east-southeast around 8 mph, gusting to 24 mph, in the morning, becoming northeast in the afternoon. Chance of precipitation 20 percent. Precipitation (liquid equivalent) mostly less than a tenth of an inch. No snow accumulation expected.
Wednesday night
 
Cloudy. Low 38°. Wind northeast around 4 mph, gusting to 21 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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