WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 03-May-2026 04:00 pm
 
Tonight

Fog late
Fog late
Monday

Thunder storm
Thunder storm
Monday
night
Thunder storm
Thunder storm
Tuesday

Thunder storm
Thunder storm
Tuesday
night
Chance rain
Chance rain
Wednesday

Fog a.m.
Fog a.m.
Wednesday
night
Mostly Cloudy
Mostly Cloudy
Thursday

Partly Cloudy
Partly Cloudy
<.1 in. <.1 in. <.25 in. .35 in. .25 in. <.1 in. <.1 in.
Low: 56° High: 78° Low: 60° High: 65° Low: 50° High: 61° Low: 46° High: 62°
               
WSW
5-28
mph
SW
9-26→12-29
mph
WSW
7-23
mph
NNE
5-23→10-27
mph
NNE
7-25
mph
NNE
7-26
mph
N→WNW
4-22
mph
WNW
7-26
mph
UV: 6
 High 
UV: 4
 Medium 
UV: 5
 Medium 
UV: 5
 Medium 

 

Tonight
 
Mostly cloudy. Patchy light fog after midnight. A chance of rain. Low 56°. Wind west-southwest around 5 mph, gusting to 28 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Monday
 
Partly cloudy. A chance of rain. Scattered thunderstorms likely, some possibly severe. High 78°. UV index up to 6. Wind southwest around 9 mph, gusting to 26 mph, in the morning, becoming 12 mph, gusting to 29 mph, in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Monday night
 
Partly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Light to moderate fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Thunderstorms very likely, some severe. Low 60°. Wind west-southwest around 7 mph, gusting to 23 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Tuesday
 
Dense overcast. Light to moderate fog in the morning. Rain likely. Thunderstorms very likely, some severe. High 65°. UV index up to 4. Wind north-northeast around 5 mph, gusting to 23 mph, in the morning, becoming 10 mph, gusting to 27 mph, in the afternoon. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Tuesday night
 
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 in the evening, then a slight chance of rain after midnight. Cool. Low 50°. Wind north-northeast around 7 mph, gusting to 25 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Wednesday
 
Mostly cloudy. Patchy light fog in the morning. A slight chance of rain. Cool. High 61°. UV index up to 5. Wind north-northeast around 7 mph, gusting to 26 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Wednesday night
 
Mostly cloudy in the evening, becoming partly to mostly cloudy after midnight. A slight chance of rain. Cool. Low 46°. Wind north around 4 mph, gusting to 22 mph, in the evening, becoming west-northwest after midnight. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Thursday
 
Sunny in the morning, becoming partly cloudy in the afternoon. Cool. High 62°. UV index up to 5. Wind west-northwest around 7 mph, gusting to 26 mph.
Thursday night
 
Partly cloudy. Cool. Low 46°. Wind southwest around 5 mph, gusting to 19 mph.
Friday
 
Mostly cloudy. A chance of rain. High 66°. UV index up to 4. Wind southwest around 7 mph, gusting to 25 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Friday night
 
Mostly cloudy in the evening, becoming fair after midnight. Patchy light fog after midnight. A chance of rain. Cool. Low 47°. Wind west-northwest around 3 mph, gusting to 18 mph, in the evening, becoming south-southwest after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Saturday
 
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. High 72°. UV index up to 8. Wind east-southeast around 6 mph, gusting to 24 mph.
Saturday night
 
Cloudy. Low 56°. Wind east-southeast around 4 mph, gusting to 21 mph, in the evening, becoming northeast after midnight.

WXSIM forecast formatting script by Saratoga-Weather.org.

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