Granville, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.5 °F (low) to 60.4 °F (high). Annual precipitation averages 36.7 Inches. 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 | 15.1 °F | 31.2 °F | 1.78 in. |
| February | 18.6 °F | 35.7 °F | 1.77 in. |
| March | 28.4 °F | 48.1 °F | 2.42 in. |
| April | 39.0 °F | 61.6 °F | 3.45 in. |
| May | 50.8 °F | 72.6 °F | 4.51 in. |
| June | 60.7 °F | 81.3 °F | 4.34 in. |
| July | 64.1 °F | 84.4 °F | 3.85 in. |
| August | 61.9 °F | 82.6 °F | 3.83 in. |
| September | 53.7 °F | 77.0 °F | 3.44 in. |
| October | 42.2 °F | 64.6 °F | 2.92 in. |
| November | 31.0 °F | 49.3 °F | 2.45 in. |
| December | 20.9 °F | 36.4 °F | 1.95 in. |
| Annual | 40.5 °F | 60.4 °F | 36.71 in. |
| 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 : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |