WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Friday, 25-Sep-2026 04:00 pm
 
Tonight

Fog
Fog
Saturday

Fog a.m.
Fog a.m.
Saturday
night
Mostly Cloudy
Mostly Cloudy
Sunday

Fog a.m.
Fog a.m.
Sunday
night
Fog late
Fog late
Monday

Fog a.m.
Fog a.m.
Monday
night
Partly Cloudy
Partly Cloudy
Tuesday

Mostly Cloudy
Mostly Cloudy
Low: 58° High: 74° Low: 56° High: 77° Low: 55° High: 77° Low: 53° High: 81°
               
E
4-21
mph
E
4-21
mph
E
3-17
mph
ESE
3-22
mph
ENE
2
mph
ENE
3-20
mph
E→SE
3
mph
SSE
6-20
mph
UV: 4
 Medium 
UV: 5
 Medium 
UV: 5
 Medium 
UV: 5
 Medium 

 

Tonight
 
Mostly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog. Low 58°. Wind east around 4 mph, gusting to 21 mph.
Saturday
 
Mostly cloudy to cloudy. Patchy light fog in the morning. High 74°. UV index up to 4. Wind east around 4 mph, gusting to 21 mph.
Saturday night
 
Mostly cloudy to cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 56°. Wind east around 3 mph, gusting to 17 mph.
Sunday
 
Partly cloudy. Patchy light fog in the morning. Warm. High 77°. UV index up to 5. Wind east-southeast around 3 mph, gusting to 22 mph.
Sunday night
 
Mostly clear in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Low 55°. Wind east-northeast around 2 mph.
Monday
 
Partly to mostly sunny. Patchy light fog in the morning. High 77°. UV index up to 5. Wind east-northeast around 3 mph, gusting to 20 mph.
Monday night
 
Clear in the evening, becoming partly cloudy after midnight. Low 53°. Wind east around 3 mph in the evening, becoming southeast after midnight.
Tuesday
 
Partly to mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. Warm. High 81°. UV index up to 5. Wind south-southeast around 6 mph, gusting to 20 mph.
Tuesday night
 
Mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. A chance of rain. Low 64°. Wind south around 5 mph, gusting to 15 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Wednesday
 
Dense overcast. Rain likely. Precipitation showery or intermittent. High 74°. Wind south around 4 mph, gusting to 16 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Wednesday night
 
Dense overcast in the evening, becoming cloudy after midnight. Patchy light fog. A chance of rain in the evening, then a slight chance of rain after midnight. Precipitation showery or intermittent. Warm. Low 69°. Wind south around 5 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Thursday
 
Dense overcast in the morning, becoming cloudy in the afternoon. Rain likely. Scattered thundershowers possible. Warm. High 79°. Wind south around 7 mph, gusting to 19 mph, in the morning, becoming 12 mph, gusting to 23 mph, in the afternoon. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch.
Thursday night
 
Cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Precipitation showery or intermittent. Warm. Low 70°. Wind south around 8 mph, gusting to 21 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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