Donnelly, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 32.7 °F (low) to 52.7 °F (high). Annual precipitation averages 26.4 Inches. Donnelly is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.7 °F | 19.8 °F | 0.7 in. |
| February | 5.1 °F | 24.1 °F | 0.75 in. |
| March | 18.6 °F | 36.9 °F | 1.25 in. |
| April | 32.2 °F | 53.5 °F | 2.25 in. |
| May | 45.6 °F | 67.4 °F | 3.12 in. |
| June | 56.5 °F | 77.1 °F | 4.17 in. |
| July | 60.4 °F | 81.0 °F | 3.87 in. |
| August | 57.3 °F | 79.1 °F | 3.16 in. |
| September | 48.5 °F | 72.0 °F | 2.74 in. |
| October | 35.6 °F | 56.8 °F | 2.43 in. |
| November | 22.0 °F | 39.7 °F | 1.03 in. |
| December | 9.1 °F | 25.5 °F | 0.88 in. |
| Annual | 32.7 °F | 52.7 °F | 26.35 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |