WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 19-Apr-2026 04:00 pm
 
Tonight

Partly Cloudy
Partly Cloudy
Monday

Sunny
Sunny
Monday
night
Partly Cloudy
Partly Cloudy
Tuesday

Partly Cloudy
Partly Cloudy
Tuesday
night
Partly Cloudy
Partly Cloudy
Wednesday

Partly Cloudy
Partly Cloudy
Wednesday
night
Partly Cloudy
Partly Cloudy
Thursday

Mostly Cloudy
Mostly Cloudy
Low: 41° High: 68° Low: 45° High: 77° Low: 49° High: 76° Low: 52° High: 79°
               
NNE
4-27
mph
E→SE
6-26
mph
SE→SSW
5-21
mph
SSW
8-27→12-30
mph
SW
8-24
mph
SW
7-24
mph
S
5-17
mph
S
9-27→13-29
mph
UV: 7
 High 
UV: 7
 High 
UV: 5
 Medium 
UV: 6
 High 

 

Tonight
 
Mostly clear in the evening, becoming fair to partly cloudy after midnight. Cool. Low 41°. Wind north-northeast around 4 mph, gusting to 27 mph.
Monday
 
Sunny. High 68°. UV index up to 7. Wind east around 6 mph, gusting to 26 mph, in the morning, becoming southeast in the afternoon.
Monday night
 
Mostly clear in the evening, becoming partly cloudy after midnight. Low 45°. Wind southeast around 5 mph, gusting to 21 mph, in the evening, becoming south-southwest after midnight.
Tuesday
 
Partly cloudy in the morning, becoming sunny in the afternoon. Warm. High 77°. UV index up to 7. Wind south-southwest around 8 mph, gusting to 27 mph, in the morning, becoming 12 mph, gusting to 30 mph, in the afternoon.
Tuesday night
 
Fair to partly cloudy in the evening, becoming clear after midnight. Low 49°. Wind southwest around 8 mph, gusting to 24 mph.
Wednesday
 
Partly cloudy. Warm. High 76°. UV index up to 5. Wind southwest around 7 mph, gusting to 24 mph.
Wednesday night
 
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Low 52°. Wind south around 5 mph, gusting to 17 mph.
Thursday
 
Partly to mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. Warm. High 79°. UV index up to 6. Wind south around 9 mph, gusting to 27 mph, in the morning, becoming 13 mph, gusting to 29 mph, in the afternoon.
Thursday night
 
Partly to mostly cloudy in the evening, becoming dense overcast after midnight. Patchy light fog after midnight. A chance of rain in the evening, then rain likely after midnight. Scattered thunderstorms likely. Low 58°. Wind south around 9 mph, gusting to 24 mph. Chance of precipitation 80 percent. Precipitation mostly between half an inch and one inch.
Friday
 
Mostly cloudy to cloudy in the morning, becoming mostly cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thundershowers possible. High 71°. UV index up to 5. Wind south-southwest around 5 mph, gusting to 19 mph, in the morning, becoming west in the afternoon. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Friday night
 
Mostly cloudy to cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Precipitation showery or intermittent. Low 52°. Wind north-northwest around 6 mph, gusting to 18 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Saturday
 
Partly to mostly cloudy in the morning, becoming dense overcast in the afternoon. Patchy light fog in the morning. A chance of rain in the afternoon. Scattered thundershowers possible. High 69°. UV index up to 6. Wind east-northeast around 7 mph, gusting to 25 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Mostly cloudy to cloudy in the evening, becoming cloudy after midnight. A slight chance of rain. Scattered thundershowers possible. Low 54°. Wind east around 8 mph, gusting to 19 mph, in the evening, becoming 4 mph after midnight. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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