Donnellson, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 44.2 °F (low) to 64.5 °F (high). Annual precipitation averages 42.5 Inches. Donnellson is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 20.6 °F | 36.6 °F | 2.77 in. |
| February | 24.3 °F | 42.0 °F | 2.32 in. |
| March | 33.2 °F | 52.9 °F | 3.14 in. |
| April | 43.5 °F | 65.6 °F | 4.85 in. |
| May | 54.4 °F | 75.5 °F | 5.03 in. |
| June | 63.2 °F | 84.3 °F | 4.47 in. |
| July | 66.5 °F | 87.3 °F | 3.99 in. |
| August | 64.1 °F | 86.1 °F | 3.36 in. |
| September | 55.9 °F | 80.4 °F | 3.15 in. |
| October | 44.4 °F | 68.3 °F | 3.27 in. |
| November | 34.4 °F | 53.2 °F | 3.53 in. |
| December | 25.7 °F | 41.5 °F | 2.62 in. |
| Annual | 44.2 °F | 64.5 °F | 42.5 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°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 |