WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 24-May-2026 04:00 pm
 
Tonight

Fog late
Fog late
Monday

Fog a.m.
Fog a.m.
Monday
night
Fog late
Fog late
Tuesday

Fog a.m.
Fog a.m.
Tuesday
night
Thunder storm
Thunder storm
Wednesday

Thunder storm
Thunder storm
Wednesday
night
Fog late
Fog late
Thursday

Thunder storm
Thunder storm
.35 in. .25 in. <.1 in. <.1 in.
Low: 58° High: 81° Low: 58° High: 82° Low: 67° High: 74° Low: 65° High: 77°
               
NNE→E
2-22
mph
E
4-23
mph
ESE
3-20
mph
SE
5-24
mph
SE
4-20
mph
E
4-18
mph
NE
4-17
mph
ENE
6-20
mph
UV: 8
 Very High 
UV: 7
 High 
UV: 5
 Medium 
UV: 5
 Medium 

 

Tonight
 
Clear. Patchy light fog after midnight. Low 58°. Wind north-northeast around 2 mph, gusting to 22 mph, in the evening, becoming east after midnight.
Monday
 
Sunny. Patchy light fog in the morning. High 81°. UV index up to 8. Wind east around 4 mph, gusting to 23 mph.
Monday night
 
Clear. Patchy light fog after midnight. Low 58°. Wind east-southeast around 3 mph, gusting to 20 mph.
Tuesday
 
Partly to mostly sunny in the morning, becoming mostly cloudy in the afternoon. Patchy light fog in the morning. High 82°. UV index up to 7. Wind southeast around 5 mph, gusting to 24 mph.
Tuesday night
 
Cloudy in the evening, becoming dense overcast after midnight. Patchy light fog after midnight. A chance of rain in the evening, then rain likely after midnight. Scattered thunderstorms likely. Low 67°. Wind southeast around 4 mph, gusting to 20 mph. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Wednesday
 
Cloudy in the morning, becoming mostly cloudy in the afternoon. Light to moderate fog in the morning, then patchy light fog in the afternoon. Rain likely. Scattered thunderstorms likely. High 74°. UV index up to 5. Wind east around 4 mph, gusting to 18 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Wednesday night
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A slight chance of rain in the evening. Precipitation showery or intermittent. Low 65°. Wind northeast around 4 mph, gusting to 17 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Thursday
 
Mostly cloudy to cloudy in the morning, becoming cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. Scattered thundershowers possible. High 77°. UV index up to 5. Wind east-northeast around 6 mph, gusting to 20 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Thursday night
 
Cloudy in the evening, becoming dense overcast after midnight. A chance of rain. Scattered thundershowers possible. Low 65°. Wind east around 5 mph, gusting to 17 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Friday
 
Dense overcast. A chance of rain. Scattered thundershowers possible. High 73°. UV index up to 4. Wind east around 5 mph, gusting to 17 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Friday night
 
Cloudy. Patchy light fog. A chance of rain. Scattered thundershowers possible. Low 65°. Wind east around 5 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Saturday
 
Dense overcast in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain. Scattered thundershowers possible. High 74°. UV index up to 9. Wind northeast around 7 mph, gusting to 26 mph, in the morning, becoming 11 mph, gusting to 29 mph, in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Fair to partly cloudy in the evening, becoming clear after midnight. Relatively cool. Low 56°. Wind northeast around 8 mph, gusting to 27 mph.

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