WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Monday, 23-Jun-2025 04:00 pm
 
Tonight

Thunder storm
Thunder storm
Tuesday

Partly Cloudy
Hot!
Partly Cloudy
Hot!
Tuesday
night
Fog late
Fog late
Wednesday

Thunder storm
Hot!
Thunder storm
Hot!
Wednesday
night
Fog late
Fog late
Thursday

Thunder storm
Hot!
Thunder storm
Hot!
Thursday
night
Thunder storm
Thunder storm
Friday

Fog a.m.
Hot!
Fog a.m.
Hot!
<.1 in. <.1 in. <.1 in. <.1 in.
Low: 75° High: 95° Low: 73° High: 92° Low: 74° High: 95° Low: 74° High: 94°
  Heat: 104°   Heat: 101°   Heat: 105°   Heat: 104°
SSW
4-23
mph
SW
5-24
mph
S
4-20
mph
SSW
5-21
mph
SW
4-17
mph
SW
5-23
mph
S
5-15
mph
SW
7-25
mph
UV: 9
 Very High 
UV: 9
 Very High 
UV: 10
 Very High 
UV: 8
 Very High 

 

Tonight
 
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thunderstorms likely, some possibly severe. Low 75°. Wind south-southwest around 4 mph, gusting to 23 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Tuesday
 
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Hot. High 95°. Heat index up to 104°. UV index up to 9. Wind southwest around 5 mph, gusting to 24 mph.
Tuesday night
 
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Light to moderate fog after midnight. Low 73°. Wind south around 4 mph, gusting to 20 mph.
Wednesday
 
Partly cloudy. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely, some possibly severe. Hot. High 92°. Heat index up to 101°. UV index up to 9. Wind south-southwest around 5 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Wednesday night
 
Partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog in the evening, then moderate fog after midnight. Low 74°. Wind southwest around 4 mph, gusting to 17 mph.
Thursday
 
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Light to moderate fog in the morning. A chance of rain in the afternoon. Thunderstorms very likely, some possibly severe. Hot. High 95°. Heat index up to 105°. UV index up to 10. Wind southwest around 5 mph, gusting to 23 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Thursday night
 
Partly cloudy in the evening, becoming mostly clear after midnight. Moderate fog. A chance of rain. Thunderstorms very likely, some possibly severe. Low 74°. Wind south around 5 mph, gusting to 15 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch.
Friday
 
Partly cloudy. Moderate fog in the morning. Hot. High 94°. Heat index up to 104°. UV index up to 8. Wind southwest around 7 mph, gusting to 25 mph.
Friday night
 
Partly to mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Light to moderate fog after midnight. Low 75°. Wind southwest around 4 mph, gusting to 20 mph.
Saturday
 
Mostly sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain in the afternoon. Scattered thunderstorms likely, some possibly severe. Hot. High 95°. Heat index up to 106°. UV index up to 9. Wind southwest around 6 mph, gusting to 26 mph. Chance of precipitation 30 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 in the evening, then moderate fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 75°. Wind south-southwest around 4 mph, gusting to 17 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Sunday
 
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Very hot. High 96°. Heat index up to 108°. UV index up to 9. Wind southwest around 5 mph, gusting to 23 mph.
Sunday night
 
Partly cloudy in the evening, becoming mostly cloudy after midnight. Low 76°. Wind southwest around 4 mph, gusting to 18 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

Powered by Davis Vantage Pro2  and   CumulusMX   v 4.4.5 (b4088)   MXUI Template v 2.2.6 by  Silver Acorn     Valid HTML5 USA Weather Finder Badge