WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Tuesday, 07-Jul-2026 05:00 am
 
Today

Partly Cloudy
Partly Cloudy
Tonight

Fog late
Fog late
Wednesday

Fog a.m.
Fog a.m.
Wednesday
night
Fog late
Fog late
Thursday

Fog a.m.
Hot!
Fog a.m.
Hot!
Thursday
night
Thunder storm
Thunder storm
Friday

Thunder storm
Hot!
Thunder storm
Hot!
Friday
night
Thunder storm
Thunder storm
<.1 in. <.1 in. <.25 in. .25 in. <.25 in.
High: 90° Low: 68° High: 91° Low: 70° High: 96° Low: 73° High: 92° Low: 75°
Heat: 94°   Heat: 96°   Heat: 103°   Heat: 102°  
N
5-25
mph
NE
2-21
mph
SSW
2-22
mph
SE→S
3-16
mph
SSW
6-24
mph
SSW
3-18
mph
SW
7-25
mph
WSW
3-16
mph
UV: 8
 Very High 
UV: 8
 Very High 
UV: 9
 Very High 
UV: 8
 Very High 

 

Today
 
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. A slight chance of rain. High 90°. Heat index up to 94°. UV index up to 8. Wind north around 5 mph, gusting to 25 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Tonight
 
Partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Low 68°. Wind northeast around 2 mph, gusting to 21 mph.
Wednesday
 
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain. Hot. High 91°. Heat index up to 96°. UV index up to 8. Wind south-southwest around 2 mph, gusting to 22 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Wednesday night
 
Mostly clear in the evening, becoming fair after midnight. Patchy light fog in the evening, then moderate fog after midnight. Low 70°. Wind southeast around 3 mph, gusting to 16 mph, in the evening, becoming south after midnight.
Thursday
 
Partly cloudy. Patchy light fog in the morning. Hot. High 96°. Heat index up to 103°. UV index up to 9. Wind south-southwest around 6 mph, gusting to 24 mph.
Thursday night
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Light to moderate fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thunderstorms likely. Low 73°. Wind south-southwest around 3 mph, gusting to 18 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Friday
 
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Moderate fog in the morning. Rain likely. Scattered thunderstorms likely. Hot. High 92°. Heat index up to 102°. UV index up to 8. Wind southwest around 7 mph, gusting to 25 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Friday night
 
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Moderate fog. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thunderstorms likely. Low 75°. Wind west-southwest around 3 mph, gusting to 16 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Saturday
 
Cloudy in the morning, becoming 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 thunderstorms likely. High 89°. Heat index up to 98°. UV index up to 6. Wind west-southwest around 4 mph, gusting to 22 mph, in the morning, becoming west-northwest in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Fair to partly cloudy in the evening, becoming fair after midnight. Light to moderate fog after midnight. Low 73°. Wind northwest around 2 mph, gusting to 20 mph, in the evening, becoming north after midnight.
Sunday
 
Partly to mostly sunny. Light to moderate fog in the morning. High 90°. Heat index up to 98°. UV index up to 9. Wind east around 6 mph, gusting to 25 mph.
Sunday night
 
Clear. Light to moderate fog after midnight. Low 71°. Wind east-northeast around 4 mph, gusting to 22 mph, in the evening, becoming near calm after midnight.
Monday
 
Sunny. Light to moderate fog in the morning. Hot. High 93°. Heat index up to 102°. UV index up to 9. Wind north-northwest around 2 mph, gusting to 21 mph, in the morning, becoming northeast in the afternoon.
Monday night
 
Clear. Light to moderate fog after midnight. Low 71°. Wind east-southeast around 3 mph, gusting to 16 mph, in the evening, becoming south-southwest after midnight.

WXSIM forecast formatting script by Saratoga-Weather.org.

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