WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 27-Sep-2026 05:00 am
 
Today

Mostly Cloudy
Mostly Cloudy
Tonight

Partly Cloudy
Partly Cloudy
Monday

Fog a.m.
Fog a.m.
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
<.1 in.
High: 75° Low: 54° High: 77° Low: 53° High: 82° Low: 57° High: 88° Low: 62°
               
ENE
3-21
mph
ENE
2-17
mph
ENE
3-22
mph
ENE→SE
2
mph
SSE
5-23
mph
SSE
6
mph
SSE
7-22
mph
SSE
6
mph
UV: 4
 Medium 
UV: 6
 High 
UV: 6
 High 
UV: 6
 High 

 

Today
 
Mostly cloudy to cloudy in the morning, becoming mostly cloudy in the afternoon. A chance of rain. High 75°. UV index up to 4. Wind east-northeast around 3 mph, gusting to 21 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Tonight
 
Partly cloudy. Low 54°. Wind east-northeast around 2 mph, gusting to 17 mph.
Monday
 
Partly to mostly sunny. Patchy light fog in the morning. Warm. High 77°. UV index up to 6. Wind east-northeast around 3 mph, gusting to 22 mph.
Monday night
 
Fair to partly cloudy. Low 53°. Wind east-northeast around 2 mph in the evening, becoming southeast after midnight.
Tuesday
 
Mostly sunny in the morning, becoming partly cloudy in the afternoon. Warm. High 82°. UV index up to 6. Wind south-southeast around 5 mph, gusting to 23 mph.
Tuesday night
 
Partly cloudy. Low 57°. Wind south-southeast around 6 mph.
Wednesday
 
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Unusually hot. High 88°. UV index up to 6. Wind south-southeast around 7 mph, gusting to 22 mph.
Wednesday night
 
Partly cloudy. Low 62°. Wind south-southeast around 6 mph.
Thursday
 
Partly to mostly cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. A chance of rain. Precipitation showery or intermittent. Warm. High 83°. UV index up to 4. Wind south-southwest around 5 mph, gusting to 18 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Thursday night
 
Mostly cloudy to cloudy in the evening, becoming dense overcast after midnight. Patchy light fog after midnight. A chance of rain. Precipitation showery or intermittent. Low 63°. Wind north around 6 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Friday
 
Dense overcast. Patchy light fog in the afternoon. Rain likely. High 65°, but temperatures falling in the afternoon. Wind north around 8 mph, gusting to 18 mph. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Friday night
 
Dense overcast. A chance of rain. Low 58°. Wind northeast around 4 mph, gusting to 17 mph, in the evening, becoming east after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Saturday
 
Dense overcast. A chance of rain. High 65°. Wind east around 5 mph, gusting to 19 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Dense overcast. Patchy light fog after midnight. A chance of rain in the evening, then rain likely after midnight. Low 57°. Wind east-southeast around 3 mph in the evening, becoming south-southeast after midnight. Chance of precipitation 80 percent. Precipitation mostly between half an inch and one inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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