WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Friday, 18-Jul-2025 04:00 pm
 
Tonight

Chance rain
Chance rain
Saturday

Thunder storm
Hot!
Thunder storm
Hot!
Saturday
night
Fog late
Fog late
Sunday

Thunder storm
Hot!
Thunder storm
Hot!
Sunday
night
Thunder storm
Thunder storm
Monday

Thunder storm
Hot!
Thunder storm
Hot!
Monday
night
Fog
Fog
Tuesday

Thunder storm
Hot!
Thunder storm
Hot!
.1 in. <.1 in. <.1 in. <.1 in. <.1 in. <.1 in.
Low: 76° High: 95° Low: 76° High: 95° Low: 74° High: 95° Low: 73° High: 96°
  Heat: 106°   Heat: 106°   Heat: 105°   Heat: 106°
SSE
3-15
mph
SSW
6-25
mph
SSW
4-20
mph
SSW→W
7-26
mph
E
3-18
mph
S→E
3-21
mph
ESE
4
mph
SE
5-23
mph
UV: 8
 Very High 
UV: 9
 Very High 
UV: 8
 Very High 
UV: 9
 Very High 

 

Tonight
 
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Moderate fog. A chance of rain in the evening, then a slight chance of rain after midnight. Low 76°. Wind south-southeast around 3 mph, gusting to 15 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Saturday
 
Partly to mostly sunny. Moderate fog in the morning. A chance of rain. Scattered thundershowers possible. Hot. High 95°. Heat index up to 106°. UV index up to 8. Wind south-southwest around 6 mph, gusting to 25 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Fair in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Low 76°. Wind south-southwest around 4 mph, gusting to 20 mph.
Sunday
 
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. A chance of rain. Scattered thundershowers possible. Hot. High 95°. Heat index up to 106°. UV index up to 9. Wind south-southwest around 7 mph, gusting to 26 mph, in the morning, becoming west in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Sunday night
 
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Low 74°. Wind east around 3 mph, gusting to 18 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Monday
 
Partly cloudy. Light to moderate fog in the morning. A chance of rain. Scattered thunderstorms likely. Hot. High 95°. Heat index up to 105°. UV index up to 8. Wind south around 3 mph, gusting to 21 mph, in the morning, becoming east in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Monday night
 
Fair to partly cloudy in the evening, becoming fair after midnight. Patchy light fog. Low 73°. Wind east-southeast around 4 mph.
Tuesday
 
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain in the afternoon. Scattered thundershowers possible. Hot. High 96°. Heat index up to 106°. UV index up to 9. Wind southeast around 5 mph, gusting to 23 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Tuesday night
 
Fair to partly cloudy in the evening, becoming clear after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A slight chance of rain. Scattered thundershowers possible. Low 74°. Wind southeast around 5 mph, gusting to 19 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Wednesday
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Light to moderate fog in the morning. Very hot. High 98°. Heat index up to 109°. UV index up to 9. Wind south around 5 mph, gusting to 22 mph.
Wednesday night
 
Clear in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Low 74°. Wind south-southeast around 5 mph, gusting to 17 mph.
Thursday
 
Sunny. Patchy light fog in the morning. Very hot. High 97°. Heat index up to 107°. UV index up to 9. Wind southwest around 5 mph, gusting to 21 mph, in the morning, becoming west in the afternoon.
Thursday night
 
Mostly clear in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. A slight chance of rain after midnight. Precipitation showery or intermittent. Low 74°. Wind south-southeast around 4 mph in the evening, becoming southwest after midnight. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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