Climate averages 1991–2020
O'Fallon weather
in April.
A mild, wet month: the 7th warmest and the 11th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
April is a mild month in O'Fallon: daytime highs average 18.7°C and nights cool to about 8.5°C. By daytime temperature it is the 7th warmest of the 12 months.
Expect about 114 mm of rain on roughly 11 days, which makes April a wet month (the 11th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 13 h 11 min on an average April day.
The nearest other city in this atlas is St. Louis (48 km away). In April its highs average 19.1°C, about as warm as O'Fallon, with 117 mm of rain.
Among the 498 cities listed in the United States, O'Fallon ranks joint 280th of 498 for the warmest April highs and joint 435th of 498 for the driest April (rainfall, lowest first). The mean April high of those 498 cities is 19.4°C; O'Fallon is 0.7°C cooler than that mean.
From April to May, average highs rise by 5.1°C to 23.8°C, and monthly rainfall rises from 114 mm to 123 mm.
The annual picture
April 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, selected | 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 | 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
April in nearby cities
- St. Louis in AprilUnited States · 48 kmHigh 19.1°C · Low 8.4°C · 117 mm rain
- Columbia (Missouri), United States in AprilUnited States · 142 kmHigh 18.5°C · Low 8.1°C · 129 mm rain
- Springfield (Illinois), United States in AprilUnited States · 143 kmHigh 17.4°C · Low 6.9°C · 116 mm rain
- Decatur in AprilUnited States · 189 kmHigh 17.2°C · Low 6.7°C · 118 mm rain
- Peoria (Illinois), United States in AprilUnited States · 230 kmHigh 16.4°C · Low 6.3°C · 112 mm rain
- Bloomington (Illinois), United States in AprilUnited States · 237 kmHigh 16.3°C · Low 5.8°C · 113 mm rain
- Champaign in AprilUnited States · 256 kmHigh 16.8°C · Low 6.1°C · 115 mm rain
- Springfield (Missouri), United States in AprilUnited States · 289 kmHigh 18.9°C · Low 8.6°C · 131 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.