O'Fallon Climate: Weather by Month and Best Time to Visit
Best months for O'Fallon: September, October.
Year at a glance
Weather by month
| Month | Avg high | Avg low | Rainfall | Rainy days | Humidity | Sunshine | Score |
|---|---|---|---|---|---|---|---|
| January | 5°C | -3°C | 75 mm | 8 | – | – | 5.0 |
| February | 8°C | -1°C | 66 mm | 8 | – | – | 5.6 |
| March | 14°C | 4°C | 97 mm | 11 | – | – | 6.3 |
| April | 20°C | 9°C | 123 mm | 12 | – | – | 7.1 |
| May | 25°C | 15°C | 129 mm | 13 | – | – | 7.1 |
| June | 30°C | 20°C | 105 mm | 11 | – | – | 7.2 |
| July | 31°C | 22°C | 86 mm | 10 | – | – | 7.0 |
| August | 31°C | 20°C | 74 mm | 9 | – | – | 7.4 |
| September | 27°C | 16°C | 81 mm | 8 | – | – | 8.1 |
| October | 21°C | 10°C | 88 mm | 8 | – | – | 7.7 |
| November | 13°C | 4°C | 94 mm | 9 | – | – | 6.4 |
| December | 7°C | -1°C | 72 mm | 9 | – | – | 5.3 |