WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Monday, 04-May-2026 05:00 am
 
Today

Thunder storm
Thunder storm
Tonight

Thunder storm
Thunder storm
Tuesday

Thunder storm
Thunder storm
Tuesday
night
Chance rain
Chance rain
Wednesday

Mostly Cloudy
Mostly Cloudy
Wednesday
night
Partly Cloudy
Partly Cloudy
Thursday

Partly Cloudy
Partly Cloudy
Thursday
night
Partly Cloudy
Partly Cloudy
<.1 in. <.1 in. .25 in. .25 in. <.1 in.
High: 82° Low: 61° High: 68° Low: 52° High: 61° Low: 43° High: 64° Low: 45°
               
SSW
5-26→11-29
mph
SW
10-27→7-17
mph
N
8-28
mph
N
7-25
mph
N
7-26
mph
N→NW
4-24
mph
W
4-25→9-26
mph
SW
6-21
mph
UV: 6
 High 
UV: 5
 Medium 
UV: 5
 Medium 
UV: 6
 High 

 

Today
 
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. A chance of rain. Scattered thunderstorms likely. Warm. High 82°. UV index up to 6. Wind south-southwest around 5 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.
Tonight
 
Partly cloudy in the evening, becoming mostly cloudy after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Thunderstorms very likely, some possibly severe. Low 61°. Wind southwest around 10 mph, gusting to 27 mph, in the evening, becoming 7 mph, gusting to 17 mph, after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Tuesday
 
Cloudy. Rain likely. Thunderstorms very likely, some possibly severe. High 68°. UV index up to 5. Wind north around 8 mph, gusting to 28 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Tuesday night
 
Cloudy. Light to moderate fog in the evening, then patchy light fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Low 52°. Wind north around 7 mph, gusting to 25 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Wednesday
 
Cloudy in the morning, becoming partly to mostly cloudy in the afternoon. A slight chance of rain. Cool. High 61°. UV index up to 5. Wind north around 7 mph, gusting to 26 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Wednesday night
 
Mostly cloudy in the evening, becoming partly cloudy after midnight. Cool. Low 43°. Wind north around 4 mph, gusting to 24 mph, in the evening, becoming northwest after midnight.
Thursday
 
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. High 64°. UV index up to 6. Wind west around 4 mph, gusting to 25 mph, in the morning, becoming 9 mph, gusting to 26 mph, in the afternoon.
Thursday night
 
Clear in the evening, becoming fair to partly cloudy after midnight. Cool. Low 45°. Wind southwest around 6 mph, gusting to 21 mph.
Friday
 
Mostly cloudy. High 69°. UV index up to 4. Wind southwest around 7 mph, gusting to 23 mph.
Friday night
 
Partly cloudy in the evening, becoming clear after midnight. Cool. Low 48°. Wind southwest around 5 mph, gusting to 20 mph.
Saturday
 
Sunny in the morning, becoming partly to mostly sunny in the afternoon. High 78°. UV index up to 7. Wind southwest around 6 mph, gusting to 25 mph.
Saturday night
 
Mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 55°. Wind southeast around 5 mph, gusting to 18 mph.
Sunday
 
Partly cloudy in the morning, becoming dense overcast in the afternoon. Light to moderate fog in the morning. A chance of rain in the afternoon. Scattered thundershowers possible. High 72°. UV index up to 6. Wind east-southeast around 7 mph, gusting to 24 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Sunday night
 
Partly to mostly cloudy in the evening, becoming dense overcast after midnight. Patchy light fog. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thunderstorms likely. Low 58°. Wind east around 4 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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