WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Tuesday, 16-Jun-2026 05:00 am
 
Today

Mostly Cloudy
Mostly Cloudy
Tonight

Fog late
Fog late
Wednesday

Thunder storm
Thunder storm
Wednesday
night
Thunder storm
Thunder storm
Thursday

Fog a.m.
Fog a.m.
Thursday
night
Fog late
Fog late
Friday

Fog a.m.
Fog a.m.
Friday
night
Fog late
Fog late
.1 in. <.25 in.
High: 81° Low: 62° High: 91° Low: 69° High: 85° Low: 63° High: 83° Low: 63°
               
WSW
10-28
mph
SW
5-24
mph
SSW
8-28→17-33
mph
SW
10-22
mph
NW
7-26
mph
NNW
3-22
mph
NNW
4-23
mph
ESE→S
5-18
mph
UV: 7
 High 
UV: 9
 Very High 
UV: 8
 Very High 
UV: 8
 Very High 

 

Today
 
Partly to mostly cloudy. High 81°. UV index up to 7. Wind west-southwest around 10 mph, gusting to 28 mph.
Tonight
 
Fair to partly cloudy. Patchy light fog after midnight. Relatively cool. Low 62°. Wind southwest around 5 mph, gusting to 24 mph.
Wednesday
 
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thundershowers possible. Breezy and hot. High 91°. UV index up to 9. Wind south-southwest around 8 mph, gusting to 28 mph, in the morning, becoming 17 mph, gusting to 33 mph, in the afternoon. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Wednesday night
 
Fair to partly cloudy in the evening, becoming clear after midnight. Moderate fog in the evening, then moderate to dense fog after midnight. A chance of rain. Scattered thundershowers possible. Low 69°. Wind southwest around 10 mph, gusting to 22 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Thursday
 
Partly to mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. Moderate fog in the morning. High 85°. UV index up to 8. Wind northwest around 7 mph, gusting to 26 mph.
Thursday night
 
Partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Relatively cool. Low 63°. Wind north-northwest around 3 mph, gusting to 22 mph.
Friday
 
Partly cloudy. Patchy light fog in the morning. High 83°. UV index up to 8. Wind north-northwest around 4 mph, gusting to 23 mph.
Friday night
 
Clear. Light to moderate fog after midnight. Relatively cool. Low 63°. Wind east-southeast around 5 mph, gusting to 18 mph, in the evening, becoming south after midnight.
Saturday
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Light to moderate fog in the morning. A slight chance of rain. High 87°. UV index up to 9. Wind south around 5 mph, gusting to 23 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Partly to mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Light to moderate fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Scattered thundershowers possible. Low 69°. Wind southeast around 4 mph, gusting to 18 mph, in the evening, becoming 7 mph after midnight. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Sunday
 
Dense overcast in the morning, becoming mostly cloudy to cloudy in the afternoon. Light to moderate fog. Rain very likely. Scattered thunderstorms likely. High 75°. UV index up to 5. Wind south-southeast around 8 mph, gusting to 18 mph, in the morning, becoming southwest in the afternoon. Chance of precipitation 80 percent. Precipitation mostly between 1 and 2 inches.
Sunday night
 
Mostly cloudy to cloudy in the evening, becoming dense overcast after midnight. Moderate fog in the evening, then light to moderate fog after midnight. Rain likely in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Low 69°. Wind northeast around 8 mph, gusting to 21 mph. Chance of precipitation 80 percent. Precipitation mostly between half an inch and one inch.
Monday
 
Dense overcast in the morning, becoming cloudy in the afternoon. Patchy light fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Precipitation showery or intermittent. Relatively cool. High 75°. UV index up to 4. Wind northeast around 7 mph, gusting to 24 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Monday night
 
Cloudy. Patchy light fog after midnight. A chance of rain. Precipitation showery or intermittent. Low 66°. Wind east-northeast around 4 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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