OFallon Missouri Weather

OFallon - Weather Data from OFallon, MO

Latitude: N 38° 50' 20" Longitude: W 90° 43' 42" Altitude: 532 ft

CDT UTC Last station update CDT

WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com

Updated: Thursday, 13-Aug-2026 05:00 am

Today Thunder storm	Tonight Thunder storm	Friday Thunder storm Hot!	Friday night Thunder storm	Saturday Fog a.m. Hot!	Saturday night Mostly Clear	Sunday Mostly Sunny Hot!	Sunday night Thunder storm
.1 in.	.1 in.	<.1 in.	<.1 in.				<.25 in.
High: 91°	Low: 72°	High: 95°	Low: 75°	High: 97°	Low: 74°	High: 99°	Low: 73°
Heat: 98°		Heat: 107°		Heat: 109°		Heat: 109°
SW 3-15 mph	SE→S 5 mph	SW 5-20 mph	ESE→SSW 5 mph	SW 7-22 mph	SW 3 mph	WSW 5-23 mph	NNW 4-16 mph
UV: 7 High		UV: 8 Very High		UV: 8 Very High		UV: 8 Very High

Today	Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. A slight chance of rain in the morning, then a chance of rain in the afternoon. Thunderstorms very likely, some severe. Hot. High 91°. Heat index up to 98°. UV index up to 7. Wind southwest around 3 mph, gusting to 15 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Tonight	Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Light to moderate fog in the evening, then moderate fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 72°. Wind southeast around 5 mph in the evening, becoming south after midnight. 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. Scattered thundershowers possible. Very hot. High 95°. Heat index up to 107°. UV index up to 8. Wind southwest around 5 mph, gusting to 20 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Friday night	Fair to partly cloudy. Light to moderate fog in the evening, then moderate fog after midnight. A chance of rain. Scattered thundershowers possible. Low 75°. Wind east-southeast around 5 mph in the evening, becoming south-southwest after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Saturday	Sunny. Patchy light fog in the morning. Very hot. High 97°. Heat index up to 109°. UV index up to 8. Wind southwest around 7 mph, gusting to 22 mph.
Saturday night	Clear in the evening, becoming mostly clear after midnight. Low 74°. Wind southwest around 3 mph.
Sunday	Partly to mostly sunny. Very hot. High 99°. Heat index up to 109°. UV index up to 8. Wind west-southwest around 5 mph, gusting to 23 mph.
Sunday night	Partly cloudy in the evening, becoming fair after midnight. Moderate fog. A chance of rain. Scattered thundershowers possible. Low 73°. Wind north-northwest around 4 mph, gusting to 16 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch.
Monday	Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain. High 85°. UV index up to 7. Wind north-northwest around 6 mph, gusting to 23 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Monday night	Partly to mostly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog in the evening, then moderate fog after midnight. Low 69°. Wind northeast around 3 mph, gusting to 16 mph, in the evening, becoming north after midnight.
Tuesday	Mostly sunny in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. High 87°. Heat index up to 92°. UV index up to 7. Wind northeast around 4 mph, gusting to 22 mph, in the morning, becoming north-northwest in the afternoon.
Tuesday night	Fair in the evening, becoming mostly cloudy to cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Precipitation showery or intermittent. Low 71°. Wind east-southeast around 6 mph, gusting to 16 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Wednesday	Mostly cloudy to cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. Hot. High 90°. Heat index up to 96°. UV index up to 6. Wind southeast around 10 mph, gusting to 25 mph.
Wednesday night	Mostly cloudy to cloudy in the evening, becoming partly to mostly cloudy after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Precipitation showery or intermittent. Low 73°. Wind south-southeast around 7 mph, gusting to 18 mph, in the evening, becoming 2 mph after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.

WXSIM forecast formatting script by Saratoga-Weather.org.

Powered by Davis Vantage Pro2 and CumulusMX v 4.6.4 (b4128) MXUI Template v 2.2.6 by Silver Acorn Valid HTML5