O'Fallon weather
Loading live data…Cloudy,much the same tomorrow
NWS, the American and the European model put O'Fallon's high today between 72° and 78°, a 6° split. Tomorrow: cloudy, around 78°, with a 1% chance of rain.
Latest for O'Fallon: NWS (National Blend (NBM)): 51° Mainly clear · American (NOAA GFS): 48° Mainly clear · European (ECMWF): 54° Partly cloudy.
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O'Fallon weather in numbers
measured normals and 10 years of recorded weatherO'Fallon swings 64°F across the year, from 88°F highs in July to 24°F lows in January, and May is usually the wettest month in a year that brings about 45 in of precipitation. Over 10 years of recorded weather it averages 141 days a year at 77°F or above, 64 of them at 86°F or above, 78 frost nights, and rain on 122 days.
Day counts are from the ERA5 reanalysis for O'Fallon’s grid square, 2016 to 2025, counted the same way for every city so the numbers compare. A reanalysis square is an area, not a weather station, so it is good for counting days and not for a single day’s record.
The weather map: all three models at once
NWS, American, European side by side around O'Fallon and nearby towns.Live rain radar →O'Fallon hourly forecast: next 14 hours
consensus of the three modelsRain in the next 24 hours, model by model
each model's own hourly precipitation, side by sideLoading the three models…
O'Fallon 10-day forecast, out to 14 days
where the models agree, and where they splitO'Fallon, Missouri (MO) is at its warmest in Jul (average highs near 88°F) and coldest in Jan (lows around 24°F), with roughly 45 in of precipitation across the year. Below, compare what NWS, American, European forecast for O'Fallon right now, and see exactly where they disagree.
We grade every model against the weather that actually happened, so you can see which forecast model is most accurate in United States before you trust any single number.
O'Fallon climate by month
average daytime high and overnight low across a typical year (1991-2020)Source: 1991-2020 averages, ERA5 for this place adjusted with NASA POWER.
How O'Fallon's weather has changed since 1995
30 years of daily data, 1995-2024, shown as changeAround O'Fallon, the difference between 1995-2004 and 2015-2024 is +1.1°F, within the normal swing from year to year.
Days above 95°F
2015-2024 against 1995-2004. Within the normal year-to-year swing
Frost nights
2015-2024 against 1995-2004, below 32°F. Within the normal year-to-year swing
Average wind
2015-2024 against 1995-2004. Within the normal year-to-year swing
Bars: each year against the area's 30-year average. Dashed lines: the average of the first and the last ten years.
See the numbers year by year
| Year | Temp vs average | Days >95°F vs avg | Frost nights vs avg | Wind vs avg |
|---|---|---|---|---|
| 1995 | −1.9°F | −11 | +10 | −2% |
| 1996 | −2.5°F | −7 | +21 | +6% |
| 1997 | −1.4°F | −0 | +10 | −2% |
| 1998 | +1.1°F | −7 | −18 | −5% |
| 1999 | +1.0°F | +17 | −1 | +1% |
| 2000 | −0.3°F | +1 | +6 | +1% |
| 2001 | +0.6°F | +11 | +2 | +1% |
| 2002 | −0.1°F | +9 | +6 | −2% |
| 2003 | −0.7°F | +8 | +6 | +1% |
| 2004 | −0.3°F | −10 | −13 | +1% |
| 2005 | +1.0°F | +19 | −1 | −5% |
| 2006 | +1.3°F | +13 | −10 | +3% |
| 2007 | +1.1°F | +10 | +9 | −2% |
| 2008 | −2.6°F | −11 | +19 | +6% |
| 2009 | −1.7°F | −11 | −3 | +1% |
| 2010 | −0.7°F | −11 | −2 | −5% |
| 2011 | +0.2°F | +3 | −3 | +1% |
| 2012 | +3.5°F | +34 | −11 | +1% |
| 2013 | −1.9°F | −2 | +22 | +1% |
| 2014 | −2.6°F | −8 | +23 | +3% |
| 2015 | −0.1°F | −11 | −20 | −2% |
| 2016 | +1.3°F | −10 | −7 | −2% |
| 2017 | +2.0°F | −1 | −20 | +1% |
| 2018 | −0.1°F | −4 | +15 | +1% |
| 2019 | −0.8°F | −11 | +7 | +1% |
| 2020 | −0.5°F | −11 | −3 | −5% |
| 2021 | +0.6°F | −9 | −9 | −2% |
| 2022 | −0.5°F | +2 | +10 | +6% |
| 2023 | +2.6°F | +14 | −23 | −2% |
| 2024 | +2.4°F | −2 | −25 | +1% |
Source: NASA POWER daily data from the MERRA-2 reanalysis, 1995-2024. Each value describes a grid square of about 50 km around O'Fallon, not a weather station, and a square that takes in sea or a large lake runs milder than the city itself. That is why this section shows change against the square's own 30-year average rather than counts you could compare with a local station. Rain and snow are left out because their long-term record in this dataset is not consistent over time. "Within the normal year-to-year swing" means the change is smaller than the usual differences between single years.
Which forecast is most accurate in O'Fallon?
CheckWeather Score, graded against the weather that actually happened
The CheckWeather Score blends temperature, wind and rain accuracy, each measured against ERA5 (the recorded weather) over the last 30 days across 1999 cities. Lower error means a higher score. See which forecast model is most accurate in United States, how we measure forecast accuracy, or which model each weather app uses.
What do you think of the forecasts?
your vote countsThe accuracy above is the measured record. This is your opinion: which forecast service do you trust most in United States? Give each 1 to 5 stars.
One vote per service. Anonymous: we store no personal data, only a one-way hash of your connection for a day to stop double votes.
Where the models disagree
temperature and rain, judged separatelyThe models often agree on temperature and still split on rain, and rain is usually what decides whether a plan survives. A wide rain range means the shower is genuinely uncertain, not that the forecast is wrong.