WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Thursday, 14-May-2026 05:00 am
 
Today

Partly Cloudy
Partly Cloudy
Tonight

Chance rain
Chance rain
Friday

Chance rain
Chance rain
Friday
night
Partly Cloudy
Partly Cloudy
Saturday

Rain likely
Rain likely
Saturday
night
Fog late
Fog late
Sunday

Fog a.m.
Fog a.m.
Sunday
night
Partly Cloudy
Partly Cloudy
.1 in. <.25 in. .35 in.
High: 76° Low: 50° High: 83° Low: 59° High: 78° Low: 63° High: 86° Low: 67°
               
SE
6-25
mph
SE
8-21
mph
SSE
9-27
mph
S
6-20
mph
SW
6-18
mph
SSE
6-15
mph
S
10-27
mph
S
10-23
mph
UV: 7
 High 
UV: 7
 High 
UV: 6
 High 
UV: 6
 High 

 

Today
 
Sunny in the morning, becoming partly cloudy in the afternoon. High 76°. UV index up to 7. Wind southeast around 6 mph, gusting to 25 mph.
Tonight
 
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. A chance of rain after midnight. Cool. Low 50°. Wind southeast around 8 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch.
Friday
 
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain. Warm. High 83°. UV index up to 7. Wind south-southeast around 9 mph, gusting to 27 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Friday night
 
Fair to partly cloudy. Low 59°. Wind south around 6 mph, gusting to 20 mph.
Saturday
 
Mostly cloudy. Rain likely. High 78°. UV index up to 6. Wind southwest around 6 mph, gusting to 18 mph. Chance of precipitation 60 percent. Precipitation mostly between a quarter and half an inch.
Saturday night
 
Fair in the evening, becoming fair to partly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. Low 63°. Wind south-southeast around 6 mph, gusting to 15 mph.
Sunday
 
Partly cloudy. Patchy light fog in the morning. Hot. High 86°. UV index up to 6. Wind south around 10 mph, gusting to 27 mph.
Sunday night
 
Mostly clear in the evening, becoming partly cloudy after midnight. Low 67°. Wind south around 10 mph, gusting to 23 mph.
Monday
 
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Rain likely. Precipitation showery or intermittent. Hot. High 86°. UV index up to 9. Wind south around 11 mph, gusting to 28 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Monday night
 
Mostly cloudy. Light to moderate fog. Rain likely in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Warm. Low 72°. Wind south around 9 mph, gusting to 20 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch.
Tuesday
 
Mostly cloudy to cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Light to moderate fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Precipitation showery or intermittent. Warm. High 82°. UV index up to 8. Wind south around 9 mph, gusting to 28 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Tuesday night
 
Mostly cloudy in the evening, becoming cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. Warm. Low 71°. Wind east around 6 mph, gusting to 23 mph, in the evening, becoming northeast after midnight.
Wednesday
 
Dense overcast in the morning, becoming mostly cloudy to cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. Scattered thundershowers possible. High 76°. UV index up to 7. Wind east around 8 mph, gusting to 27 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Wednesday night
 
Cloudy in the evening, becoming dense overcast after midnight. Light to moderate fog. Rain likely. Scattered thundershowers possible. Low 67°. Wind east-southeast around 6 mph, gusting to 23 mph. Chance of precipitation 80 percent. Precipitation mostly between half an inch and one inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

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