WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Wednesday, 10-Jun-2026 04:00 pm
 
Tonight

Thunder storm
Thunder storm
Thursday

Thunder storm
Thunder storm
Thursday
night
Chance rain
Chance rain
Friday

Sunny
Sunny
Friday
night
Fog late
Fog late
Saturday

Thunder storm
Thunder storm
Saturday
night
Thunder storm
Thunder storm
Sunday

Chance rain
Chance rain
.1 in. <.1 in. .1 in. .1 in. .75 in. <.25 in.
Low: 75° High: 90° Low: 68° High: 85° Low: 65° High: 86° Low: 70° High: 79°
  Heat: 98°            
SSW
7-22
mph
SSW
9-27→13-28
mph
WSW→NW
11-24→7-17
mph
NW
4-22
mph
S
3-17
mph
S
8-26
mph
S→WNW
5-22
mph
NW
9-26
mph
UV: 9
 Very High 
UV: 9
 Very High 
UV: 9
 Very High 
UV: 8
 Very High 

 

Tonight
 
Partly cloudy. Moderate fog. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thunderstorms likely, some possibly severe. Low 75°. Wind south-southwest around 7 mph, gusting to 22 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Thursday
 
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning. A slight chance of rain in the afternoon. Scattered thundershowers possible. Hot. High 90°. Heat index up to 98°. UV index up to 9. Wind south-southwest around 9 mph, gusting to 27 mph, in the morning, becoming 13 mph, gusting to 28 mph, in the afternoon. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Thursday night
 
Partly cloudy. Patchy light fog. A chance of rain. Low 68°. Wind west-southwest around 11 mph, gusting to 24 mph, in the evening, becoming northwest around 7 mph, gusting to 17 mph, after midnight. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Friday
 
Sunny. High 85°. UV index up to 9. Wind northwest around 4 mph, gusting to 22 mph.
Friday night
 
Clear in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 65°. Wind south around 3 mph, gusting to 17 mph.
Saturday
 
Partly to mostly cloudy. Patchy light fog in the morning. A chance of rain. Scattered thundershowers possible. High 86°. UV index up to 9. Wind south around 8 mph, gusting to 26 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Saturday night
 
Mostly cloudy in the evening, becoming cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Scattered thunderstorms likely. Low 70°. Wind south around 5 mph, gusting to 22 mph, in the evening, becoming west-northwest after midnight. Chance of precipitation 70 percent. Precipitation mostly between half an inch and one inch.
Sunday
 
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain. Precipitation showery or intermittent. High 79°. UV index up to 8. Wind northwest around 9 mph, gusting to 26 mph. Chance of precipitation 40 percent. Precipitation mostly less than a quarter of an inch.
Sunday night
 
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Relatively cool. Low 62°. Wind north-northwest around 3 mph, gusting to 22 mph, in the evening, becoming west-northwest after midnight.
Monday
 
Partly cloudy. High 81°. UV index up to 8. Wind west around 4 mph, gusting to 23 mph.
Monday night
 
Partly cloudy. Relatively cool. Low 61°. Wind southwest around 4 mph, gusting to 18 mph, in the evening, becoming west after midnight.
Tuesday
 
Sunny in the morning, becoming partly to mostly cloudy in the afternoon. High 82°. UV index up to 10. Wind west around 5 mph, gusting to 24 mph.
Tuesday night
 
Fair in the evening, becoming clear after midnight. Patchy light fog after midnight. Relatively cool. Low 61°. Wind west around 4 mph, gusting to 20 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

Powered by Davis Vantage Pro2  and   CumulusMX   v 4.6.4 (b4128)   MXUI Template v 2.2.6 by  Silver Acorn     Valid HTML5 USA Weather Finder Badge