WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Thursday, 26-Mar-2026 05:00 am
 
Today

Mostly Sunny
Mostly Sunny
Tonight

Thunder storm
Thunder storm
Friday

Mostly Cloudy
Mostly Cloudy
Friday
night
Mostly Clear
Mostly Clear
Saturday

Sunny
Sunny
Saturday
night
Partly Cloudy
Partly Cloudy
Sunday

Mostly Cloudy
Mostly Cloudy
Sunday
night
Partly Cloudy
Partly Cloudy
.25 in.
High: 96° Low: 52° High: 61° Low: 37° High: 61° Low: 44° High: 74° Low: 47°
               
SW
11-32
mph
NNW
8-23→12-30
mph
N
12-31
mph
N
8-28→5-19
mph
E→SE
6-26
mph
SSE
7-24
mph
SSE
8-27
mph
S
9-23
mph
UV: 7
 High 
UV: 7
 High 
UV: 7
 High 
UV: 6
 High 

 

Today
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Near record heat. High 96°. UV index up to 7. Wind southwest around 11 mph, gusting to 32 mph.
Tonight
 
Partly to mostly cloudy in the evening, becoming dense overcast after midnight. A slight chance of rain in the evening, then rain likely after midnight. Scattered thundershowers possible. Low 52°. Wind north-northwest around 8 mph, gusting to 23 mph, in the evening, becoming 12 mph, gusting to 30 mph, after midnight. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Friday
 
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Breezy. High 61°. UV index up to 7. Wind north around 12 mph, gusting to 31 mph.
Friday night
 
Mostly clear. Low 37°. Wind north around 8 mph, gusting to 28 mph, in the evening, becoming 5 mph, gusting to 19 mph, after midnight.
Saturday
 
Sunny. High 61°. UV index up to 7. Wind east around 6 mph, gusting to 26 mph, in the morning, becoming southeast in the afternoon.
Saturday night
 
Partly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Low 44°. Wind south-southeast around 7 mph, gusting to 24 mph.
Sunday
 
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Warm. High 74°. UV index up to 6. Wind south-southeast around 8 mph, gusting to 27 mph.
Sunday night
 
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Low 47°. Wind south around 9 mph, gusting to 23 mph.
Monday
 
Partly cloudy. Breezy and unusually hot. High 85°. UV index up to 7. Wind south-southwest around 11 mph, gusting to 30 mph.
Monday night
 
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Mild. Low 58°. Wind south-southwest around 11 mph, gusting to 22 mph.
Tuesday
 
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Breezy and exceptionally hot. High 88°. UV index up to 6. Wind south-southwest around 12 mph, gusting to 32 mph.
Tuesday night
 
Partly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thunderstorms likely. Breezy and mild. Low 62°. Wind south-southwest around 13 mph, gusting to 24 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Wednesday
 
Dense overcast. Patchy light fog. Rain likely. Thunderstorms very likely, some possibly severe. High 66°. Wind south-southwest around 7 mph, gusting to 22 mph, in the morning, becoming north in the afternoon. Chance of precipitation 70 percent. Precipitation mostly around a quarter of an inch.
Wednesday night
 
Dense overcast. Patchy light fog. Rain likely. Scattered thundershowers possible. Low 51°. Wind north-northeast around 7 mph, gusting to 20 mph. Chance of precipitation 80 percent. Precipitation mostly around an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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