Granville, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.7 °C (low) to 15.8 °C (high). Annual precipitation averages 932.4 Millimeters. Granville is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.4 °C | -0.4 °C | 45.21 mm |
| February | -7.4 °C | 2.1 °C | 44.96 mm |
| March | -2 °C | 8.9 °C | 61.47 mm |
| April | 3.9 °C | 16.4 °C | 87.63 mm |
| May | 10.4 °C | 22.6 °C | 114.55 mm |
| June | 15.9 °C | 27.4 °C | 110.24 mm |
| July | 17.8 °C | 29.1 °C | 97.79 mm |
| August | 16.6 °C | 28.1 °C | 97.28 mm |
| September | 12.1 °C | 25 °C | 87.38 mm |
| October | 5.7 °C | 18.1 °C | 74.17 mm |
| November | -0.6 °C | 9.6 °C | 62.23 mm |
| December | -6.2 °C | 2.4 °C | 49.53 mm |
| Annual | 4.7 °C | 15.8 °C | 932.44 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 |