WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Wednesday, 29-Apr-2026 05:00 am
 
Today

Mostly Cloudy
Mostly Cloudy
Tonight

Mostly Cloudy
Mostly Cloudy
Thursday

Mostly Cloudy
Mostly Cloudy
Thursday
night
Chance rain
Chance rain
Friday

Partly Cloudy
Partly Cloudy
Friday
night
Partly Cloudy
Partly Cloudy
Saturday

Mostly Sunny
Mostly Sunny
Saturday
night
Clear
Clear
.1 in.
High: 65° Low: 44° High: 66° Low: 45° High: 60° Low: 40° High: 59° Low: 40°
               
NW
9-28→12-29
mph
NW
8-26→3-16
mph
WSW
2-27→5-24
mph
WNW
5-20
mph
N
9-27
mph
N
4-23
mph
N
5-26→10-27
mph
NW→WSW
4-24
mph
UV: 5
 Medium 
UV: 6
 High 
UV: 6
 High 
UV: 6
 High 

 

Today
 
Partly to mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. High 65°. UV index up to 5. Wind northwest around 9 mph, gusting to 28 mph, in the morning, becoming 12 mph, gusting to 29 mph, in the afternoon.
Tonight
 
Partly to mostly cloudy in the evening, becoming fair after midnight. Cool. Low 44°. Wind northwest around 8 mph, gusting to 26 mph, in the evening, becoming 3 mph, gusting to 16 mph, after midnight.
Thursday
 
Mostly sunny in the morning, becoming mostly cloudy in the afternoon. High 66°. UV index up to 6. Wind west-southwest around 2 mph, gusting to 27 mph, in the morning, becoming 5 mph, gusting to 24 mph, in the afternoon.
Thursday night
 
Cloudy in the evening, becoming partly to mostly cloudy after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Precipitation showery or intermittent. Cool. Low 45°. Wind west-northwest around 5 mph, gusting to 20 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Friday
 
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Cool. High 60°. UV index up to 6. Wind north around 9 mph, gusting to 27 mph.
Friday night
 
Partly cloudy in the evening, becoming fair after midnight. Cool. Low 40°. Wind north around 4 mph, gusting to 23 mph.
Saturday
 
Partly to mostly sunny. Cool. High 59°. UV index up to 6. Wind north around 5 mph, gusting to 26 mph, in the morning, becoming 10 mph, gusting to 27 mph, in the afternoon.
Saturday night
 
Clear. Unusually cold. Low 40°. Wind northwest around 4 mph, gusting to 24 mph, in the evening, becoming west-southwest after midnight.
Sunday
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. High 69°. UV index up to 7. Wind west-southwest around 8 mph, gusting to 28 mph, in the morning, becoming 13 mph, gusting to 30 mph, in the afternoon.
Sunday night
 
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. Light to moderate fog after midnight. Rain likely. Scattered thundershowers possible. Cool. Low 48°. Wind west-southwest around 8 mph, gusting to 22 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Monday
 
Partly cloudy. Patchy light fog in the morning. Breezy. High 74°. UV index up to 6. Wind west-southwest around 9 mph, gusting to 29 mph, in the morning, becoming 13 mph, gusting to 31 mph, in the afternoon.
Monday night
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Scattered thundershowers possible. Low 55°. Wind west-southwest around 10 mph, gusting to 24 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Tuesday
 
Partly to mostly cloudy in the morning, becoming dense overcast in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Thunderstorms very likely, some possibly severe. High 69°. Wind west-southwest around 7 mph, gusting to 20 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Tuesday night
 
Mostly cloudy to cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Thunderstorms very likely, some possibly severe. Low 59°. Wind south-southeast around 5 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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