WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Friday, 03-Jul-2026 04:00 pm
 
Tonight

Thunder storm
Thunder storm
Saturday

Thunder storm
Hot!
Thunder storm
Hot!
Saturday
night
Thunder storm
Thunder storm
Sunday

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

Thunder storm
Thunder storm
Monday
night
Chance rain
Chance rain
Tuesday

Chance rain
Chance rain
.25 in. .1 in. <.1 in. <.1 in. .1 in. <.1 in. <.1 in. <.1 in.
Low: 76° High: 93° Low: 76° High: 90° Low: 74° High: 88° Low: 72° High: 88°
  Heat: 105°   Heat: 101°   Heat: 95°   Heat: 93°
SE
4-21
mph
WSW
5-24
mph
SSE→W
2-19
mph
WNW
3-23
mph
N
2-19
mph
N
4-22
mph
N
4-20
mph
NE
4-24
mph
UV: 8
 Very High 
UV: 9
 Very High 
UV: 6
 High 
UV: 8
 Very High 

 

Tonight
 
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Thunderstorms very likely, some possibly severe. Low 76°. Wind southeast around 4 mph, gusting to 21 mph. Chance of precipitation 70 percent. Precipitation mostly around a quarter of an inch.
Saturday
 
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Moderate fog in the morning. Rain likely. Thunderstorms very likely, some severe. Hot. High 93°. Heat index up to 105°. UV index up to 8. Wind west-southwest around 5 mph, gusting to 24 mph. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch.
Saturday night
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog. A chance of rain. Scattered thunderstorms likely. Low 76°. Wind south-southeast around 2 mph, gusting to 19 mph, in the evening, becoming west after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Sunday
 
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Light to moderate fog in the morning. A chance of rain. Thunderstorms very likely, some possibly severe. Hot. High 90°. Heat index up to 101°. UV index up to 9. Wind west-northwest around 3 mph, gusting to 23 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch.
Sunday night
 
Partly cloudy. Light to moderate fog in the evening, then moderate fog after midnight. Rain likely. Scattered thunderstorms likely. Low 74°. Wind north around 2 mph, gusting to 19 mph. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch.
Monday
 
Partly cloudy. Moderate fog in the morning. A chance of rain. Scattered thundershowers possible. High 88°. Heat index up to 95°. UV index up to 6. Wind north around 4 mph, gusting to 22 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch.
Monday night
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Low 72°. Wind north around 4 mph, gusting to 20 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Tuesday
 
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. High 88°. Heat index up to 93°. UV index up to 8. Wind northeast around 4 mph, gusting to 24 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Tuesday night
 
Mostly clear in the evening, becoming fair after midnight. Light to moderate fog after midnight. Low 70°. Wind northeast around 3 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. Hot. High 91°. Heat index up to 98°. UV index up to 8. Wind east-southeast around 3 mph, gusting to 20 mph.
Wednesday night
 
Partly to mostly cloudy. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 74°. Wind south-southeast around 3 mph, gusting to 17 mph, in the evening, becoming south-southwest after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Thursday
 
Partly cloudy. Light to moderate fog in the morning. Rain likely. Thunderstorms very likely, some possibly severe. Hot. High 91°. Heat index up to 99°. UV index up to 9. Wind west-southwest around 4 mph, gusting to 22 mph. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch.
Thursday night
 
Fair to partly cloudy. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain. Scattered thunderstorms likely, some possibly severe. Low 71°. Wind northwest around 3 mph, gusting to 19 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.

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