Griggsville, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.8 °F (low) to 62.9 °F (high). Annual precipitation averages 39.2 Inches. Griggsville is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 18.4 °F | 35.1 °F | 2.07 in. |
| February | 22.0 °F | 40.2 °F | 1.9 in. |
| March | 31.3 °F | 51.5 °F | 2.77 in. |
| April | 41.8 °F | 64.0 °F | 4.02 in. |
| May | 53.2 °F | 73.7 °F | 4.57 in. |
| June | 62.5 °F | 82.3 °F | 4.66 in. |
| July | 65.7 °F | 85.8 °F | 4.4 in. |
| August | 63.4 °F | 84.8 °F | 3.26 in. |
| September | 54.8 °F | 78.8 °F | 3.61 in. |
| October | 43.4 °F | 66.4 °F | 2.94 in. |
| November | 33.1 °F | 52.3 °F | 2.87 in. |
| December | 23.7 °F | 40.0 °F | 2.13 in. |
| Annual | 42.8 °F | 62.9 °F | 39.2 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |