WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 02-Aug-2026 05:00 am
 
Today

Chance rain
Chance rain
Tonight

Fog late
Fog late
Monday

Fog a.m.
Fog a.m.
Monday
night
Fog
Fog
Tuesday

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

Partly Cloudy
Partly Cloudy
Wednesday
night
Fog late
Fog late
<.1 in. <.1 in. <.1 in. <.1 in.
High: 80° Low: 62° High: 83° Low: 63° High: 87° Low: 66° High: 91° Low: 69°
            Heat: 95°  
NNW
9-27
mph
NNE
4-20
mph
NNE
3-21
mph
ENE→SE
3
mph
SE
4-22
mph
SE
5-18
mph
SSE
5-23
mph
ENE→NNE
5-17
mph
UV: 7
 High 
UV: 8
 Very High 
UV: 8
 Very High 
UV: 8
 Very High 

 

Today
 
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. A chance of rain. High 80°. UV index up to 7. Wind north-northwest around 9 mph, gusting to 27 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Tonight
 
Fair to partly cloudy in the evening, becoming fair after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain. Relatively cool. Low 62°. Wind north-northeast around 4 mph, gusting to 20 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Monday
 
Mostly 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 83°. UV index up to 8. Wind north-northeast around 3 mph, gusting to 21 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Monday night
 
Fair in the evening, becoming clear after midnight. Patchy light fog. Relatively cool. Low 63°. Wind east-northeast around 3 mph in the evening, becoming southeast after midnight.
Tuesday
 
Sunny. Patchy light fog in the morning. High 87°. UV index up to 8. Wind southeast around 4 mph, gusting to 22 mph.
Tuesday night
 
Fair to partly cloudy. Relatively cool. Low 66°. Wind southeast around 5 mph, gusting to 18 mph.
Wednesday
 
Sunny in the morning, becoming partly cloudy in the afternoon. Hot. High 91°. Heat index up to 95°. UV index up to 8. Wind south-southeast around 5 mph, gusting to 23 mph.
Wednesday night
 
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Low 69°. Wind east-northeast around 5 mph, gusting to 17 mph, in the evening, becoming north-northeast after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Thursday
 
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. A chance of rain. High 88°. Heat index up to 93°. UV index up to 8. Wind east around 3 mph, gusting to 21 mph, in the morning, becoming northwest in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Thursday night
 
Partly to mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 70°. Wind north-northeast around 2 mph, gusting to 18 mph, in the evening, becoming east after midnight.
Friday
 
Mostly cloudy to cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. High 87°. Heat index up to 92°. UV index up to 6. Wind east around 4 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Friday night
 
Mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Light to moderate fog. Rain likely. Scattered thundershowers possible. Low 71°. Wind south-southwest around 6 mph, gusting to 20 mph. Chance of precipitation 60 percent. Precipitation mostly between a quarter and half an inch.
Saturday
 
Partly to mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Hot. High 94°. Heat index up to 101°. UV index up to 9. Wind south-southwest around 5 mph, gusting to 22 mph.
Saturday night
 
Mostly clear. Patchy light fog after midnight. Low 71°. Wind southwest around 5 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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