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O'Fallon, IL Weather
Current conditions
Observed at St. Louis Downtown Airport · 19 min ago
Forecast
10-day-
Today
Sunny, with a high near 73. Southeast wind around 3 mph.
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Tonight
Mostly clear, with a low around 46. East wind around 3 mph.
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Wednesday
Sunny, with a high near 74. East wind around 2 mph.
National Weather Service forecast updated 5 hrs ago.
Hourly
Hourly forecast- Now71°
- 6 PM67°
- 7 PM62°
- 8 PM58°
- 9 PM56°
- 10 PM55°
- 11 PM53°
- Wed12 AM52°
- 1 AM51°
- 2 AM49°
- 3 AM49°
- 4 AM48°
- 5 AM47°
- 6 AM47°
- 7 AM47°
- 8 AM49°
- 9 AM55°
- 10 AM61°
- 11 AM65°
- 12 PM69°
- 1 PM72°
- 2 PM72°
- 3 PM73°
- 4 PM73°
10-day forecast
Details- TodayOct 20Sunny46°73°
- WedOct 21Sunny49°74°
- ThuOct 22Sunny49°76°
- FriOct 23Sunny48°75°
- SatOct 24Mostly Sunny51°76°
- SunOct 25Partly Sunny51°77°
- MonOct 26Partly Sunny48°75°
- TueOct 27Cloudy56°69°
- WedOct 28Rain0.09 in51°60°
- ThuOct 29Cloudy0.02 in49°61°
Days after the National Weather Service's seven are MET Norway's outlook, a computer model with no forecaster's review.
Radar
Full mapWeather news in Illinois
More weather news-
Another beautiful day ahead for Central IllinoisDECATUR, Ill. (WAND) – If you’re looking for a reason to get outside, Tuesday is your day. A high-pressure system settling over the Midwest is bringing abundant sunshine and calm winds to Central Illinois, with…
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One of the year’s most pleasant weather stretches arrives in Central IllinoisDECATUR, Ill. (WAND) – A beautiful stretch of sunshine and mild temperatures is settling into the region, and it’s the perfect time to get outside and enjoy it. High pressure is taking control of the Midwest, locking in…
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A great week ahead for Central IllinoisWAND DECATUR, Ill. (WAND) – A wonderful weekend across Central Illinois carries into the start of the workweek. Overnight lows dip back into the upper 30s tonight with a small risk for patchy frost, though coverage will…
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Sunshine, chilly mornings and a big warm-up ahead for central IllinoisCENTRAL ILLINOIS (25News Now) - Fall is making an appearance across central Illinois this weekend, but don’t get too comfortable with the chilly temperatures. After a cold start on Sunday morning, sunshine will help…
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Overnight Frost Advisory for parts of Illinois, NW IndianaCBS News Colorado 10pm Saturday CBS News Detroit Weekend 11pm CBS News Los Angeles Weekend 9pm CBS News Philadelphia Weekend 11pm KDKA News Weekend 11pm CBS News Texas Weekend 10pm
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Frost advisory back in effect for Central IllinoisWAND DECATUR, Ill. (WAND) – Another cool day starts the weekend across Central Illinois with highs Saturday only reaching the upper 50s under plenty of sunny skies. Strong high pressure remains in control keeping skies…
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Frosty Nights Ahead Before a Warm-Up Arrives in Central IllinoisCENTRAL ILLINOIS (25News Now) - Central Illinois is in for a chilly weekend, with temperatures dropping into the 30s and frost possible overnight. But after a cool start to the weekend, a warming trend will bring…
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Dangerous Freeze Warnings Issued for Iowa, Wisconsin, Minnesota and Illinois as Temperatures DropFreeze Warnings take effect early Saturday across much of Iowa, Wisconsin, southeast and central Minnesota and northern Illinois, with lows as cold as 26 degrees expected. Seven National Weather Service offices issued…
Air quality
Air quality is satisfactory, and air pollution poses little or no risk.
Forecast
- TueModerate
- WedModerate
- ThuModerate
St. Louis (Metro-east), IL reporting area · 1 hr ago. Data from AirNow (EPA and its state, local and tribal partners); preliminary and subject to change.
Sun & moon
Almanac
MonthlyBelleville Siu Research, records since 1948. Normals 1991–2020. Data from NOAA's Regional Climate Centers (ACIS).
Nearby
- St. Louis 25 km
- Saint Charles 54 km
- Florissant 42 km
- Chesterfield 58 km
- Belleville 10 km
- Oakville 37 km
- University City 35 km
- Ballwin 55 km
- Upper Alton 41 km
- Granite City 24 km
- Mehlville 37 km
- Kirkwood 43 km
Forecasters' discussion
From the National Weather Service office in LSX, issued 10 hrs ago
Key Messages
- Dry and seasonably warm conditions will persist through the end of the week.
Short Term
Issued at 227 AM CDT Tue Oct 20 2026
The forecast for the next several days can be summed up in one phrase - status quo. With an omega block in place in the mid-levels and high pressure stationed over the eastern CONUS at the surface, there is no reason for our sensible weather to change. The small increases in temperature we expect over the week can be attributed to persistent insolation rather than any sort of advection or dynamical reasoning. High clouds blowing into the region from the southern Plains may enter Mid-Missouri slightly before peak heating, which would prevent that area from gaining that degree or two of warmth this afternoon - a negligible difference on human skin. In all, the forecast today calls for highs around 70 degrees with very little wind and plenty of sun. Add a degree and we have the forecast for Wednesday as well. The high clouds and warmer afternoon will support higher low temperatures tonight for our Missouri counties. To the east where skies will be clearer for longer, radiational cooling is expected to create similar conditions to this morning.
Long Term
Issued at 227 AM CDT Tue Oct 20 2026
The forecast from Wednesday night through the end of the week is the same as that of today and tomorrow. Widespread 70s increase a degree or two each day unless warming is perturbed by high clouds. Late in the week mid-level ridging will be shoved eastward and flattened as a longwave trough strengthens over the Four Corners region. This system is forecast to drive a cold front into the Midwest late Saturday into Sunday, but latest model guidance indicates the front will pivot into a more west-east orientation before it reaches Missouri/central Illinois. This would keep accompanying rain and cold air to our north and lengthen the duration of our warm streak. Ensembles, aside from the GEFS, appear to support this solution. 850 mb temperatures Sunday into Monday are still forecast to be about 10C - the same as today - so a drastic cooldown within that period is not likely if the models are correct. Beyond that guidance diverges, and that's reliant on if the cold front does push through the CWA or not Monday into Tuesday. The NBM high temperature IQRs reflect the uncertainty quite well, with KSTL jumping from a 4 degree split on Sunday to a 12 degree split by Tuesday.
Aviation
Issued at 604 AM CDT Tue Oct 20 2026
After the morning river and valley fog dissipates, dry and VFR conditions with light winds will prevail through the remainder of the period.
Forecasts, observations and alerts in the United States come from the National Weather Service (NOAA); radar from NOAA's Multi-Radar Multi-Sensor system; satellite imagery from NASA's Global Imagery Browse Services (GIBS) and NOAA's GOES satellites; the map from the U.S. Geological Survey's National Map; air quality from AirNow (EPA and its partners); hurricane information from the National Hurricane Center; climate normals and records from NOAA's Regional Climate Centers (ACIS). Forecasts outside the United States and the UV index: MET Norway (CC BY 4.0); observations outside the U.S.: airport reports via NOAA's Aviation Weather Center. Place names: GeoNames (CC BY 4.0). Data are copied on a schedule and may lag the sources; for warnings that affect your safety, follow your local National Weather Service office and emergency officials. Weather news is drawn from the 4Conservative index and reflects what the press published. Terms of use.