Richmond, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.4 °C (low) to 14.1 °C (high). Annual precipitation averages 951.2 Millimeters. Richmond is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.3 °C | -1.7 °C | 45.21 mm |
| February | -8.8 °C | 0.5 °C | 46.99 mm |
| March | -3.7 °C | 6.8 °C | 55.12 mm |
| April | 2.1 °C | 13.9 °C | 96.01 mm |
| May | 8.2 °C | 20.3 °C | 112.01 mm |
| June | 13.8 °C | 25.8 °C | 122.94 mm |
| July | 16.3 °C | 28 °C | 95 mm |
| August | 15.3 °C | 27.1 °C | 97.03 mm |
| September | 11 °C | 23.4 °C | 91.69 mm |
| October | 4.7 °C | 16.1 °C | 77.47 mm |
| November | -1.2 °C | 8.2 °C | 61.21 mm |
| December | -6.9 °C | 1.2 °C | 50.55 mm |
| Annual | 3.4 °C | 14.1 °C | 951.23 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |