WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Tuesday, 29-Sep-2026 04:00 pm
 
Tonight

Mostly Cloudy
Mostly Cloudy
Wednesday

Mostly Cloudy
Mostly Cloudy
Wednesday
night
Mostly Cloudy
Mostly Cloudy
Thursday

Rain likely
Rain likely
Thursday
night
Rain likely
Rain likely
Friday

Rain likely
Rain likely
Friday
night
Fog late
Fog late
Saturday

Fog a.m.
Fog a.m.
1.0 in. 2.0 in. .75 in.
Low: 62° High: 89° Low: 67° High: 85° Low: 64° High: 71° Low: 54° High: 72°
               
SSE
5-20
mph
S
7-24
mph
SSE
6-16
mph
SSE→WSW
6-22
mph
WNW→N
2→6-19
mph
NNE
9-25
mph
NNE
6-21
mph
NE
5-21
mph
UV: 6
 High 
UV: 4
 Medium 
UV: 6
 High 
UV: 6
 High 

 

Tonight
 
Partly to mostly cloudy in the evening, becoming mostly cloudy after midnight. Low 62°. Wind south-southeast around 5 mph, gusting to 20 mph.
Wednesday
 
Partly to mostly cloudy. Unusually hot. High 89°. UV index up to 6. Wind south around 7 mph, gusting to 24 mph.
Wednesday night
 
Mostly cloudy to cloudy. Warm. Low 67°. Wind south-southeast around 6 mph, gusting to 16 mph.
Thursday
 
Mostly cloudy to cloudy in the morning, becoming cloudy in the afternoon. Light to moderate fog in the afternoon. A slight chance of rain in the morning, then rain likely in the afternoon. Precipitation showery or intermittent. Unusually hot. High 85°. UV index up to 4. Wind south-southeast around 6 mph, gusting to 22 mph, in the morning, becoming west-southwest in the afternoon. Chance of precipitation 70 percent. Precipitation mostly around an inch.
Thursday night
 
Dense overcast. Light to moderate fog. Rain likely. Precipitation showery or intermittent. Mild. Low 64°. Wind west-northwest around 2 mph in the evening, becoming north around 6 mph, gusting to 19 mph, after midnight. Chance of precipitation 80 percent. Precipitation mostly around 2 inches.
Friday
 
Mostly cloudy in the morning, becoming mostly sunny in the afternoon. Light to moderate fog in the morning. Rain likely. High 71°. UV index up to 6. Wind north-northeast around 9 mph, gusting to 25 mph. Chance of precipitation 70 percent. Precipitation mostly between half an inch and one inch.
Friday night
 
Clear. Patchy light fog in the evening, then moderate fog after midnight. Low 54°. Wind north-northeast around 6 mph, gusting to 21 mph.
Saturday
 
Sunny. Moderate fog in the morning. High 72°. UV index up to 6. Wind northeast around 5 mph, gusting to 21 mph.
Saturday night
 
Clear. Patchy light fog in the evening, then light to moderate fog after midnight. Low 52°. Wind east-northeast around 2 mph in the evening, becoming north after midnight.
Sunday
 
Sunny. Light to moderate fog in the morning. High 72°. UV index up to 6. Wind north-northwest around 4 mph, gusting to 20 mph.
Sunday night
 
Clear. Patchy light fog in the evening, then moderate fog after midnight. Low 53°. Wind north-northwest around 6 mph, gusting to 16 mph.
Monday
 
Sunny. Light to moderate fog in the morning. High 67°. UV index up to 5. Wind northeast around 7 mph, gusting to 25 mph.
Monday night
 
Clear. Patchy light fog after midnight. Low 49°. Wind east-northeast around 5 mph, gusting to 18 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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