WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 14-Dec-2025 04:00 pm
 
Tonight

Partly Cloudy
Partly Cloudy
Monday

Mostly Sunny
Mostly Sunny
Monday
night
Partly Cloudy
Partly Cloudy
Tuesday

Mostly Cloudy
Mostly Cloudy
Tuesday
night
Mostly Cloudy
Mostly Cloudy
Wednesday

Mostly Cloudy
Mostly Cloudy
Wednesday
night
Chance rain
Chance rain
Thursday

Rain likely
Rain likely
<.1 in. .5 in.
Low: 8° High: 41° Low: 22° High: 51° Low: 31° High: 54° Low: 42° High: 48°
WCh: -2°   WCh: 16°          
SSE
calm→5
mph
S→SW
8-22
mph
SW
5
mph
SW
7-21
mph
SW
6
mph
WSW→SSE
2
mph
SSE
7→11-17
mph
WSW
13-29
mph

 

Tonight
 
Fair to partly cloudy. Cold. Low 8°. Wind chill ranging from -2 to 15. Wind south-southeast near calm in the evening, becoming 5 mph after midnight.
Monday
 
Partly to mostly sunny. High 41°. Wind south around 8 mph, gusting to 22 mph, in the morning, becoming southwest in the afternoon.
Monday night
 
Fair to partly cloudy. Low 22°. Wind chill ranging from 16 to 30. Wind southwest around 5 mph.
Tuesday
 
Partly to mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. Relatively mild. High 51°. Wind southwest around 7 mph, gusting to 21 mph.
Tuesday night
 
Mostly cloudy. Low 31°. Wind southwest around 6 mph.
Wednesday
 
Partly to mostly cloudy. Relatively mild. High 54°. Wind west-southwest around 2 mph in the morning, becoming south-southeast in the afternoon.
Wednesday night
 
Cloudy in the evening, becoming dense overcast after midnight. A chance of rain after midnight. Relatively mild. Low 42°, but temperatures rising after midnight. Wind south-southeast around 7 mph in the evening, becoming 11 mph, gusting to 17 mph, after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Thursday
 
Dense overcast in the morning, becoming partly cloudy in the afternoon. Patchy light fog. Rain likely in the morning, then a slight chance of rain in the afternoon. Breezy. High 48°. Wind west-southwest around 13 mph, gusting to 29 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch.
Thursday night
 
Mostly clear in the evening, becoming clear after midnight. Breezy. Low 23°. Wind west around 15 mph, gusting to 29 mph, in the evening, becoming 9 mph, gusting to 27 mph, after midnight.
Friday
 
Sunny in the morning, becoming partly cloudy in the afternoon. High 43°. Wind west around 3 mph, gusting to 18 mph, in the morning, becoming south around 6 mph, gusting to 23 mph, in the afternoon.
Friday night
 
Fair to partly cloudy in the evening, becoming fair after midnight. Low 26°. Wind chill ranging from 18 to 32. Wind south around 10 mph, gusting to 20 mph.
Saturday
 
Mostly sunny in the morning, becoming cloudy in the afternoon. Breezy and relatively mild. High 49°. Wind south around 11 mph, gusting to 20 mph.
Saturday night
 
Dense overcast in the evening, becoming mostly cloudy to cloudy after midnight. A chance of rain in the evening, then a slight chance of a mix of rain, sleet, freezing rain, and snow after midnight. Low 29°. Wind chill ranging from 22 to 39. Wind west-southwest around 6 mph in the evening, becoming north-northwest around 12 mph, gusting to 18 mph, after midnight. Chance of precipitation 50 percent. Precipitation (liquid equivalent) mostly around a tenth of an inch. Little or no snow or ice (on ground) accumulation expected. Little if any freezing rain accumulation.

WXSIM forecast formatting script by Saratoga-Weather.org.

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