WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 29-Mar-2026 05:00 am
 
Today

Partly Cloudy
Partly Cloudy
Tonight

Partly Cloudy
Partly Cloudy
Monday

Sunny
Sunny
Monday
night
Partly Cloudy
Partly Cloudy
Tuesday

Thunder storm
Thunder storm
Tuesday
night
Thunder storm
Thunder storm
Wednesday

Thunder storm
Thunder storm
Wednesday
night
Thunder storm
Thunder storm
<.25 in. .75 in. .75 in. 1.0 in.
High: 73° Low: 45° High: 83° Low: 54° High: 84° Low: 55° High: 56° Low: 48°
               
S
6-26→10-28
mph
S
8-23
mph
S
11-29
mph
SSW
10-22
mph
SSW
13-31
mph
WSW→N
6-16
mph
NE
6
mph
NE→S
5
mph
UV: 6
 High 
UV: 7
 High 
UV: 5
 Medium 

 

Today
 
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Warm. High 73°. UV index up to 6. Wind south around 6 mph, gusting to 26 mph, in the morning, becoming 10 mph, gusting to 28 mph, in the afternoon.
Tonight
 
Partly cloudy in the evening, becoming fair after midnight. Low 45°. Wind south around 8 mph, gusting to 23 mph.
Monday
 
Sunny. Unusually hot. High 83°. UV index up to 7. Wind south around 11 mph, gusting to 29 mph.
Monday night
 
Partly cloudy. Low 54°. Wind south-southwest around 10 mph, gusting to 22 mph.
Tuesday
 
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. A chance of rain in the afternoon. Scattered thunderstorms likely. Breezy and unusually hot. High 84°. UV index up to 5. Wind south-southwest around 13 mph, gusting to 31 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Tuesday night
 
Mostly cloudy in the evening, becoming cloudy after midnight. Moderate fog. Rain likely. Scattered thundershowers possible. Low 55°. Wind west-southwest around 6 mph, gusting to 16 mph, in the evening, becoming north after midnight. Chance of precipitation 70 percent. Precipitation mostly between half an inch and one inch.
Wednesday
 
Dense overcast. Patchy light fog in the morning, then light to moderate fog in the afternoon. Rain likely. Scattered thundershowers possible. High 56°, but temperatures falling in the afternoon. Wind northeast around 6 mph. Chance of precipitation 80 percent. Precipitation mostly between half an inch and one inch.
Wednesday night
 
Dense overcast. Light to moderate fog. Rain likely. Scattered thundershowers possible. Low 48°, but temperatures rising after midnight. Wind northeast around 5 mph in the evening, becoming south after midnight. Chance of precipitation 80 percent. Precipitation mostly around an inch.
Thursday
 
Dense overcast. Light to moderate fog in the morning. Rain likely in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely. High 64°. Wind south-southwest around 9 mph, gusting to 21 mph. Chance of precipitation 80 percent. Precipitation mostly around half an inch.
Thursday night
 
Cloudy. Patchy light fog. A chance of rain. Scattered thundershowers possible. Mild. Low 59°. Wind south-southwest around 6 mph, gusting to 20 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Friday
 
Cloudy in the morning, becoming mostly cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thundershowers possible. Mild. High 69°. Wind northeast around 3 mph, gusting to 18 mph, in the morning, becoming east-southeast in the afternoon. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Friday night
 
Mostly cloudy to cloudy in the evening, becoming cloudy after midnight. Patchy light fog. A chance of rain. Scattered thundershowers possible. Mild. Low 62°. Wind southeast around 7 mph, gusting to 18 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Saturday
 
Cloudy in the morning, becoming dense overcast in the afternoon. Patchy light fog in the morning, then light to moderate fog in the afternoon. A chance of rain in the morning, then rain likely in the afternoon. Thunderstorms very likely, some possibly severe. Mild. High 69°. UV index up to 4. Wind south-southeast around 9 mph, gusting to 23 mph, in the morning, becoming west-southwest in the afternoon. Chance of precipitation 80 percent. Precipitation mostly around half an inch.
Saturday night
 
Dense overcast. Patchy light fog. Rain likely in the evening, then a slight chance of rain after midnight. Scattered thunderstorms likely. Low 51°. Wind west-northwest around 10 mph, gusting to 27 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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