WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Monday, 21-Sep-2026 04:00 pm
 
Tonight

Mostly Cloudy
Mostly Cloudy
Tuesday

Mostly Cloudy
Mostly Cloudy
Tuesday
night
Partly Cloudy
Partly Cloudy
Wednesday

Mostly Sunny
Mostly Sunny
Wednesday
night
Partly Cloudy
Partly Cloudy
Thursday

Mostly Sunny
Mostly Sunny
Thursday
night
Partly Cloudy
Partly Cloudy
Friday

Mostly Cloudy
Mostly Cloudy
Low: 63° High: 74° Low: 55° High: 75° Low: 53° High: 77° Low: 56° High: 74°
               
NE
4-16
mph
NE
6-24
mph
NE
6-23
mph
N
6-25
mph
NE
4-22
mph
NE
4-24
mph
NE
2-17
mph
E
4-18
mph
UV: 6
 High 
UV: 6
 High 

 

Tonight
 
Mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Low 63°. Wind northeast around 4 mph, gusting to 16 mph.
Tuesday
 
Mostly cloudy to cloudy in the morning, becoming mostly cloudy in the afternoon. High 74°. Wind northeast around 6 mph, gusting to 24 mph.
Tuesday night
 
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Low 55°. Wind northeast around 6 mph, gusting to 23 mph.
Wednesday
 
Partly to mostly sunny. High 75°. UV index up to 6. Wind north around 6 mph, gusting to 25 mph.
Wednesday night
 
Fair in the evening, becoming partly cloudy after midnight. Low 53°. Wind northeast around 4 mph, gusting to 22 mph.
Thursday
 
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. High 77°. UV index up to 6. Wind northeast around 4 mph, gusting to 24 mph.
Thursday night
 
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. Low 56°. Wind northeast around 2 mph, gusting to 17 mph.
Friday
 
Mostly cloudy in the morning, becoming cloudy in the afternoon. High 74°. Wind east around 4 mph, gusting to 18 mph.
Friday night
 
Mostly cloudy to cloudy in the evening, becoming mostly cloudy after midnight. Low 59°. Wind east-southeast around 4 mph.
Saturday
 
Cloudy. A slight chance of rain in the morning, then a chance of rain in the afternoon. High 74°. Wind east-southeast around 5 mph, gusting to 18 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Mostly cloudy to cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Low 60°. Wind east-southeast around 5 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Sunday
 
Partly to mostly cloudy in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Warm. High 82°. UV index up to 5. Wind south around 6 mph, gusting to 22 mph, in the morning, becoming west in the afternoon.
Sunday night
 
Fair. Moderate fog after midnight. Low 57°. Wind north around 5 mph, gusting to 16 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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