WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Friday, 20-Jun-2025 04:00 pm
 
Tonight

Fog late
Fog late
Saturday

Fog a.m.
Hot!
Fog a.m.
Hot!
Saturday
night
Fog late
Fog late
Sunday

Fog a.m.
Hot!
Fog a.m.
Hot!
Sunday
night
Fog late
Fog late
Monday

Fog a.m.
Hot!
Fog a.m.
Hot!
Monday
night
Thunder storm
Thunder storm
Tuesday

Thunder storm
Hot!
Thunder storm
Hot!
.1 in. <.25 in.
Low: 74° High: 93° Low: 77° High: 96° Low: 76° High: 97° Low: 76° High: 90°
  Heat: 102°   Heat: 109°   Heat: 109°   Heat: 102°
S
8-23
mph
S
11-28
mph
S
8-24
mph
SSW
9-27
mph
SSW
6-22
mph
SSW
6-25
mph
S
5-21
mph
S
3-17
mph
UV: 10
 Very High 
UV: 10
 Very High 
UV: 10
 Very High 
UV: 7
 High 

 

Tonight
 
Clear. Patchy light fog in the evening, then moderate fog after midnight. Low 74°. Wind south around 8 mph, gusting to 23 mph.
Saturday
 
Sunny. Moderate fog in the morning. Hot. High 93°. Heat index up to 102°. UV index up to 10. Wind south around 11 mph, gusting to 28 mph.
Saturday night
 
Clear. Patchy light fog in the evening, then moderate fog after midnight. Low 77°. Wind south around 8 mph, gusting to 24 mph.
Sunday
 
Sunny. Moderate fog in the morning. Very hot. High 96°. Heat index up to 109°. UV index up to 10. Wind south-southwest around 9 mph, gusting to 27 mph.
Sunday night
 
Clear. Moderate fog after midnight. Low 76°. Wind south-southwest around 6 mph, gusting to 22 mph.
Monday
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Light to moderate fog in the morning. Very hot. High 97°. Heat index up to 109°. UV index up to 10. Wind south-southwest around 6 mph, gusting to 25 mph.
Monday night
 
Partly cloudy. Patchy light fog in the evening, then moderate fog after midnight. Rain likely. Scattered thundershowers possible. Low 76°. Wind south around 5 mph, gusting to 21 mph. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch.
Tuesday
 
Partly to mostly cloudy. Light to moderate fog in the morning. Rain likely. Scattered thunderstorms likely. Hot. High 90°. Heat index up to 102°. UV index up to 7. Wind south around 3 mph, gusting to 17 mph. Chance of precipitation 70 percent. Precipitation mostly less than a quarter of an inch.
Tuesday night
 
Moderate fog. Rain likely. Scattered thunderstorms likely. Low 77°. Wind south around 4 mph. Chance of precipitation 70 percent. Precipitation mostly less than a quarter of an inch.
Wednesday
 
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 morning, then a chance of rain in the afternoon. Scattered thunderstorms likely. Hot. High 94°. Heat index up to 106°. UV index up to 9. Wind southwest around 5 mph, gusting to 23 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch.
Wednesday night
 
Fair to partly cloudy in the evening, becoming clear after midnight. Moderate fog in the evening, then moderate to dense fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 76°. Wind southwest around 5 mph, gusting to 16 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Thursday
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Moderate fog in the morning. A chance of rain in the afternoon. Scattered thunderstorms likely, some possibly severe. Hot. High 95°. Heat index up to 109°. UV index up to 9. Wind southwest around 4 mph, gusting to 22 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Thursday night
 
Partly to mostly cloudy in the evening, becoming mostly clear after midnight. Moderate fog in the evening, then moderate to dense fog after midnight. A chance of rain. Thunderstorms very likely, some severe. Low 75°. Wind southeast around 4 mph in the evening, becoming southwest after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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