WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 26-Apr-2026 04:00 pm
 
Tonight

Partly Cloudy
Partly Cloudy
Monday

Thunder storm
Thunder storm
Monday
night
Thunder storm
Thunder storm
Tuesday

Fog a.m.
Fog a.m.
Tuesday
night
Rain likely
Rain likely
Wednesday

Fog a.m.
Fog a.m.
Wednesday
night
Clear
Clear
Thursday

Partly Cloudy
Partly Cloudy
<.25 in. .1 in. .5 in.
Low: 62° High: 82° Low: 58° High: 77° Low: 54° High: 66° Low: 45° High: 66°
               
SE
9-26
mph
SE→SSW
13-31→17-33
mph
W
11-27→7-19
mph
WNW
5-28
mph
NNE
7-23
mph
NNW
11-28
mph
NNW
5-26
mph
NNW
4-23
mph
UV: 5
 Medium 
UV: 7
 High 
UV: 6
 High 
UV: 6
 High 

 

Tonight
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 62°. Wind southeast around 9 mph, gusting to 26 mph.
Monday
 
Mostly cloudy. A slight chance of rain in the morning, then a chance of rain in the afternoon. Thunderstorms very likely, some severe. Breezy and warm. High 82°. UV index up to 5. Wind southeast around 13 mph, gusting to 31 mph, in the morning, becoming south-southwest around 17 mph, gusting to 33 mph, in the afternoon. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Monday night
 
Fair in the evening, becoming mostly clear after midnight. Light to moderate fog. A chance of rain. Scattered thundershowers possible. Low 58°. Wind west around 11 mph, gusting to 27 mph, in the evening, becoming 7 mph, gusting to 19 mph, after midnight. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Tuesday
 
Sunny in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning. Warm. High 77°. UV index up to 7. Wind west-northwest around 5 mph, gusting to 28 mph.
Tuesday night
 
Mostly cloudy in the evening, becoming partly to mostly cloudy after midnight. Moderate fog. Rain likely in the evening, then a chance of rain after midnight. Precipitation showery or intermittent. Low 54°. Wind north-northeast around 7 mph, gusting to 23 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch.
Wednesday
 
Sunny in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning. High 66°. UV index up to 6. Wind north-northwest around 11 mph, gusting to 28 mph.
Wednesday night
 
Clear. Cool. Low 45°. Wind north-northwest around 5 mph, gusting to 26 mph.
Thursday
 
Mostly sunny in the morning, becoming partly cloudy in the afternoon. High 66°. UV index up to 6. Wind north-northwest around 4 mph, gusting to 23 mph.
Thursday night
 
Mostly cloudy. Patchy light fog after midnight. A chance of rain. Low 48°. Wind west-northwest around 3 mph, gusting to 16 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Friday
 
Partly to mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. High 63°. UV index up to 6. Wind northwest around 6 mph, gusting to 27 mph, in the morning, becoming 10 mph, gusting to 27 mph, in the afternoon.
Friday night
 
Clear. Cool. Low 43°. Wind north around 6 mph, gusting to 26 mph, in the evening, becoming east-northeast around 2 mph after midnight.
Saturday
 
Sunny. High 67°. UV index up to 9. Wind southwest around 3 mph, gusting to 30 mph, in the morning, becoming west-northwest in the afternoon.
Saturday night
 
Clear in the evening, becoming partly cloudy after midnight. Low 49°. Wind south around 5 mph, gusting to 16 mph, in the evening, becoming 8 mph, gusting to 17 mph, after midnight.

WXSIM forecast formatting script by Saratoga-Weather.org.

Powered by Davis Vantage Pro2  and   CumulusMX   v 4.6.4 (b4128)   MXUI Template v 2.2.6 by  Silver Acorn     Valid HTML5 USA Weather Finder Badge