WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Friday, 31-Jul-2026 05:00 am
 
Today

Rain likely
Rain likely
Tonight

Rain likely
Rain likely
Saturday

Thunder storm
Thunder storm
Saturday
night
Thunder storm
Thunder storm
Sunday

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

Fog a.m.
Fog a.m.
Monday
night
Fog late
Fog late
.35 in. .5 in. .25 in. <.25 in.
High: 84° Low: 74° High: 78° Low: 69° High: 80° Low: 65° High: 85° Low: 64°
               
S
7-23→10-25
mph
S→SW
8-24
mph
W
11-27
mph
NNW
12-27
mph
NNW
11-27
mph
NNW
5-24
mph
N
5-24
mph
NE
3-19
mph
UV: 5
 Medium 
UV: 6
 High 
UV: 9
 Very High 

 

Today
 
Mostly cloudy to cloudy. Rain likely. Precipitation showery or intermittent. High 84°. UV index up to 5. Wind south around 7 mph, gusting to 23 mph, in the morning, becoming 10 mph, gusting to 25 mph, in the afternoon. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Tonight
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Moderate fog. Rain likely in the evening, then a chance of rain after midnight. Precipitation showery or intermittent. Low 74°. Wind south around 8 mph, gusting to 24 mph, in the evening, becoming southwest after midnight. Chance of precipitation 70 percent. Precipitation mostly around half an inch.
Saturday
 
Cloudy in the morning, becoming dense overcast in the afternoon. Patchy light fog in the morning. Rain likely. Scattered thundershowers possible. High 78°. Wind west around 11 mph, gusting to 27 mph. Chance of precipitation 70 percent. Precipitation mostly around a quarter of an inch.
Saturday night
 
Cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Patchy light fog. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thundershowers possible. Breezy. Low 69°. Wind north-northwest around 12 mph, gusting to 27 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Sunday
 
Mostly cloudy to cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. High 80°. UV index up to 6. Wind north-northwest around 11 mph, gusting to 27 mph.
Sunday night
 
Mostly clear. Light to moderate fog after midnight. Relatively cool. Low 65°. Wind north-northwest around 5 mph, gusting to 24 mph.
Monday
 
Sunny. Patchy light fog in the morning. High 85°. UV index up to 9. Wind north around 5 mph, gusting to 24 mph.
Monday night
 
Clear. Patchy light fog after midnight. Relatively cool. Low 64°. Wind northeast around 3 mph, gusting to 19 mph.
Tuesday
 
Sunny. Patchy light fog in the morning. High 85°. UV index up to 9. Wind east-northeast around 3 mph, gusting to 24 mph.
Tuesday night
 
Clear. Patchy light fog after midnight. Relatively cool. Low 66°. Wind east-northeast around 3 mph, gusting to 19 mph, in the evening, becoming southeast after midnight.
Wednesday
 
Sunny. Patchy light fog in the morning. High 89°. Heat index up to 93°. UV index up to 9. Wind south-southeast around 3 mph, gusting to 21 mph, in the morning, becoming east in the afternoon.
Wednesday night
 
Clear in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Low 67°. Wind east-southeast around 5 mph, gusting to 19 mph.
Thursday
 
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Very hot. High 97°. Heat index up to 103°. UV index up to 9. Wind southeast around 7 mph, gusting to 22 mph, in the morning, becoming south in the afternoon.
Thursday night
 
Partly to mostly 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. Scattered thunderstorms likely. Low 74°. Wind east-southeast around 7 mph in the evening, becoming south after midnight. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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