Climate averages 1991–2020
O'Fallon weather
in June.
A hot, wet month: the 3rd warmest and the 10th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
June is a hot month in O'Fallon: daytime highs average 28.6°C and nights cool to about 19.3°C. By daytime temperature it is the 3rd warmest of the 12 months.
Expect about 101 mm of rain on roughly 11 days, which makes June a wet month (the 10th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 14 h 50 min on an average June day.
The nearest other city in this atlas is St. Louis (48 km away). In June its highs average 29.1°C, about as warm as O'Fallon, with 106 mm of rain.
Among the 498 cities listed in the United States, O'Fallon ranks joint 212th of 498 for the warmest June highs and joint 340th of 498 for the driest June (rainfall, lowest first). The mean June high of those 498 cities is 27.9°C; O'Fallon is 0.7°C warmer than that mean.
From June to July, average highs rise by 2.2°C to 30.8°C, and monthly rainfall falls from 101 mm to 82 mm.
The annual picture
June in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
O'Fallon climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 4.0°C-4.4°C | -4.4°C | 65 | 7.7 | 9.810 h |
| February | 6.8°C-2.6°C | -2.6°C | 61 | 7.7 | 10.711 h |
| March | 12.6°C2.6°C | 2.6°C | 92 | 10.6 | 11.912 h |
| April | 18.7°C8.5°C | 8.5°C | 114 | 11.3 | 13.213 h |
| May | 23.8°C14.3°C | 14.3°C | 123 | 13.3 | 14.314 h |
| June, selected | 28.6°C19.3°C | 19.3°C | 101 | 11.0 | 14.815 h |
| July | 30.8°C21.6°C | 21.6°C | 82 | 9.9 | 14.615 h |
| August | 30.1°C20.9°C | 20.9°C | 76 | 9.1 | 13.714 h |
| September | 26.0°C16.7°C | 16.7°C | 81 | 7.6 | 12.512 h |
| October | 19.5°C10.4°C | 10.4°C | 84 | 8.4 | 11.211 h |
| November | 12.0°C3.7°C | 3.7°C | 89 | 8.3 | 10.110 h |
| December | 6.1°C-1.7°C | -1.7°C | 62 | 7.8 | 9.510 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
June in nearby cities
- St. Louis in JuneUnited States · 48 kmHigh 29.1°C · Low 19.3°C · 106 mm rain
- Columbia (Missouri), United States in JuneUnited States · 142 kmHigh 28.8°C · Low 19.1°C · 113 mm rain
- Springfield (Illinois), United States in JuneUnited States · 143 kmHigh 27.4°C · Low 18.0°C · 110 mm rain
- Decatur in JuneUnited States · 189 kmHigh 27.1°C · Low 17.9°C · 110 mm rain
- Peoria (Illinois), United States in JuneUnited States · 230 kmHigh 26.9°C · Low 17.8°C · 111 mm rain
- Bloomington (Illinois), United States in JuneUnited States · 237 kmHigh 26.5°C · Low 17.2°C · 110 mm rain
- Champaign in JuneUnited States · 256 kmHigh 26.7°C · Low 17.3°C · 105 mm rain
- Springfield (Missouri), United States in JuneUnited States · 289 kmHigh 28.6°C · Low 18.9°C · 101 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for O'Fallon) is explained once on the O'Fallon year overview and on the Sources, method and limits page.