WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Thursday, 24-Sep-2026 04:00 pm
 
Tonight

Fog
Fog
Friday

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

Chance rain
Chance rain
Saturday
night
Fog late
Fog late
Sunday

Chance rain
Chance rain
Sunday
night
Fog late
Fog late
Monday

Fog a.m.
Fog a.m.
.1 in. .1 in.
Low: 53° High: 71° Low: 56° High: 71° Low: 56° High: 72° Low: 55° High: 74°
               
NE
2-18
mph
ESE
4-16
mph
ENE
4-15
mph
ESE
3-17
mph
ESE
3
mph
ESE
3-15
mph
ESE
3
mph
ESE
4-17
mph
UV: 5
 Medium 
UV: 4
 Medium 

 

Tonight
 
Partly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog. Low 53°. Wind northeast around 2 mph, gusting to 18 mph.
Friday
 
Mostly cloudy in the morning, becoming dense overcast in the afternoon. Patchy light fog in the morning. High 71°. Wind east-southeast around 4 mph, gusting to 16 mph.
Friday night
 
Mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Low 56°. Wind east-northeast around 4 mph, gusting to 15 mph.
Saturday
 
Mostly cloudy to cloudy in the morning, becoming cloudy in the afternoon. A chance of rain. High 71°. Wind east-southeast around 3 mph, gusting to 17 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Saturday night
 
Mostly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. Low 56°. Wind east-southeast around 3 mph.
Sunday
 
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. High 72°. UV index up to 5. Wind east-southeast around 3 mph, gusting to 15 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Sunday night
 
Fair to partly cloudy. Patchy light fog in the evening, then light to moderate fog after midnight. Low 55°. Wind east-southeast around 3 mph.
Monday
 
Partly cloudy. Light to moderate fog in the morning. High 74°. UV index up to 4. Wind east-southeast around 4 mph, gusting to 17 mph.
Monday night
 
Partly cloudy. Patchy light fog after midnight. Low 56°. Wind southeast around 4 mph.
Tuesday
 
Partly to mostly cloudy in the morning, becoming mostly cloudy in the afternoon. Warm. High 80°. UV index up to 5. Wind south-southeast around 5 mph, gusting to 16 mph.
Tuesday night
 
Mostly cloudy to cloudy in the evening, becoming dense overcast after midnight. Patchy light fog after midnight. A slight chance of rain in the evening, then rain likely after midnight. Low 64°. Wind south-southeast around 4 mph in the evening, becoming southwest after midnight. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Wednesday
 
Dense overcast. Patchy light fog. Rain likely in the morning, then a chance of rain in the afternoon. High 73°. Wind south-southeast around 5 mph. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Wednesday night
 
Mostly cloudy to cloudy in the evening, becoming cloudy after midnight. Warm. Low 68°. Wind east-southeast around 7 mph in the evening, becoming south-southeast after midnight.

WXSIM forecast formatting script by Saratoga-Weather.org.

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