Donnelly, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.4 °C (low) to 11.5 °C (high). Annual precipitation averages 669.3 Millimeters. 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 | -16.8 °C | -6.8 °C | 17.78 mm |
| February | -14.9 °C | -4.4 °C | 19.05 mm |
| March | -7.4 °C | 2.7 °C | 31.75 mm |
| April | 0.1 °C | 11.9 °C | 57.15 mm |
| May | 7.6 °C | 19.7 °C | 79.25 mm |
| June | 13.6 °C | 25.1 °C | 105.92 mm |
| July | 15.8 °C | 27.2 °C | 98.3 mm |
| August | 14.1 °C | 26.2 °C | 80.26 mm |
| September | 9.2 °C | 22.2 °C | 69.6 mm |
| October | 2 °C | 13.8 °C | 61.72 mm |
| November | -5.6 °C | 4.3 °C | 26.16 mm |
| December | -12.7 °C | -3.6 °C | 22.35 mm |
| Annual | 0.4 °C | 11.5 °C | 669.29 mm |
| 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 : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |