WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Thursday, 09-Jul-2026 05:00 am
 
Today

Chance rain
Chance rain
Tonight

Chance rain
Chance rain
Friday

Thunder storm
Thunder storm
Friday
night
Thunder storm
Thunder storm
Saturday

Chance rain
Chance rain
Saturday
night
Fog late
Fog late
Sunday

Fog a.m.
Fog a.m.
Sunday
night
Fog late
Fog late
.1 in. <.25 in. <.25 in. .25 in. <.1 in.
High: 92° Low: 73° High: 88° Low: 75° High: 86° Low: 70° High: 88° Low: 68°
Heat: 98°   Heat: 95°   Heat: 92°   Heat: 93°  
WSW
4-22
mph
S
3-16
mph
WSW
4-22
mph
WNW→NNE
3-16
mph
NNE
6-26
mph
NNE
4-23
mph
NE
4-23→7-24
mph
NE
5-23
mph
UV: 9
 Very High 
UV: 8
 Very High 
UV: 8
 Very High 
UV: 9
 Very High 

 

Today
 
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. A slight chance of rain in the morning, then a chance of rain in the afternoon. Hot. High 92°. Heat index up to 98°. UV index up to 9. Wind west-southwest around 4 mph, gusting to 22 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Tonight
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain. Precipitation showery or intermittent. Low 73°. Wind south around 3 mph, gusting to 16 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Friday
 
Mostly cloudy. Moderate fog in the morning. Rain likely. Scattered thunderstorms likely. High 88°. Heat index up to 95°. UV index up to 8. Wind west-southwest around 4 mph, gusting to 22 mph. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch.
Friday night
 
Partly to mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Moderate fog in the evening, then light to moderate fog after midnight. Rain likely. Scattered thundershowers possible. Low 75°. Wind west-northwest around 3 mph, gusting to 16 mph, in the evening, becoming north-northeast after midnight. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Saturday
 
Mostly cloudy to cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain. High 86°. Heat index up to 92°. UV index up to 8. Wind north-northeast around 6 mph, gusting to 26 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Mostly clear in the evening, becoming clear after midnight. Light to moderate fog after midnight. Low 70°. Wind north-northeast around 4 mph, gusting to 23 mph.
Sunday
 
Sunny. Light to moderate fog in the morning. High 88°. Heat index up to 93°. UV index up to 9. Wind northeast around 4 mph, gusting to 23 mph, in the morning, becoming 7 mph, gusting to 24 mph, in the afternoon.
Sunday night
 
Clear. Patchy light fog after midnight. Relatively cool. Low 68°. Wind northeast around 5 mph, gusting to 23 mph.
Monday
 
Sunny. Patchy light fog in the morning. High 89°. Heat index up to 93°. UV index up to 9. Wind northeast around 6 mph, gusting to 25 mph.
Monday night
 
Clear. Patchy light fog after midnight. Relatively cool. Low 67°. Wind northeast around 5 mph, gusting to 22 mph, in the evening, becoming 2 mph after midnight.
Tuesday
 
Sunny in the morning, becoming mostly sunny in the afternoon. Patchy light fog in the morning. Hot. High 92°. Heat index up to 96°. UV index up to 9. Wind north around 4 mph, gusting to 22 mph, in the morning, becoming northeast in the afternoon.
Tuesday night
 
Mostly clear in the evening, becoming clear after midnight. Patchy light fog after midnight. Low 68°. Wind northeast around 3 mph, gusting to 18 mph, in the evening, becoming east-southeast after midnight.
Wednesday
 
Sunny in the morning, becoming mostly sunny in the afternoon. Patchy light fog in the morning. Hot. High 90°. Heat index up to 96°. UV index up to 9. Wind east-southeast around 4 mph, gusting to 23 mph.
Wednesday night
 
Clear. Light to moderate fog after midnight. Low 70°. Wind east-southeast around 5 mph, gusting to 20 mph, in the evening, becoming south after midnight.

WXSIM forecast formatting script by Saratoga-Weather.org.

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