WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Saturday, 23-May-2026 05:00 am
 
Today

Chance rain
Chance rain
Tonight

Thunder storm
Thunder storm
Sunday

Thunder storm
Thunder storm
Sunday
night
Fog late
Fog late
Monday

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

Thunder storm
Thunder storm
Tuesday
night
Thunder storm
Thunder storm
<.1 in. .25 in. <.1 in. <.1 in. <.1 in. .1 in.
High: 79° Low: 63° High: 78° Low: 60° High: 81° Low: 66° High: 73° Low: 68°
               
WSW
2-20
mph
SSW→W
2
mph
NNW
4-21
mph
ENE
1-16
mph
E
4-22
mph
E
4-19
mph
ESE
6-18
mph
ESE
5-16
mph
UV: 6
 High 
UV: 6
 High 
UV: 8
 Very High 

 

Today
 
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. A chance of rain. Precipitation showery or intermittent. High 79°. UV index up to 6. Wind west-southwest around 2 mph, gusting to 20 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Tonight
 
Mostly cloudy to cloudy. Patchy light fog in the evening, then light to moderate fog after midnight. Rain likely. Scattered thundershowers possible. Low 63°. Wind south-southwest around 2 mph in the evening, becoming west after midnight. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Sunday
 
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thundershowers possible. High 78°. UV index up to 6. Wind north-northwest around 4 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Sunday night
 
Mostly clear in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 60°. Wind east-northeast around 1 mph, gusting to 16 mph.
Monday
 
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain. High 81°. UV index up to 8. Wind east around 4 mph, gusting to 22 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Monday night
 
Fair to partly cloudy in the evening, becoming cloudy after midnight. Low 66°. Wind east around 4 mph, gusting to 19 mph.
Tuesday
 
Dense overcast. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thundershowers possible. High 73°. Wind east-southeast around 6 mph, gusting to 18 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Tuesday night
 
Dense overcast. Patchy light fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 68°. Wind east-southeast around 5 mph, gusting to 16 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Wednesday
 
Cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning, then light to moderate fog in the afternoon. Rain likely. Scattered thunderstorms likely. High 75°. UV index up to 7. Wind southeast around 5 mph, gusting to 17 mph. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Wednesday 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. A chance of rain. Scattered thunderstorms likely. Low 67°. Wind southeast around 4 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Thursday
 
Mostly cloudy. Moderate fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely. High 78°. UV index up to 6. Wind east-southeast around 5 mph, gusting to 16 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Thursday night
 
Mostly cloudy in the evening, becoming dense overcast after midnight. Patchy light fog. A chance of rain. Scattered thunderstorms likely. Low 68°. Wind south-southeast around 3 mph in the evening, becoming west-southwest after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Friday
 
Cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. Light to moderate fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely, some possibly severe. High 79°. UV index up to 5. Wind west around 6 mph, gusting to 19 mph, in the morning, becoming 9 mph, gusting to 21 mph, in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Friday 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. Rain likely. Thunderstorms very likely, some severe. Low 65°. Wind north-northeast around 5 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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