Willmar, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.7 °F (low) to 53.2 °F (high). Annual precipitation averages 29.4 Inches. Willmar 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 | 3.1 °F | 20.9 °F | 0.71 in. |
| February | 6.4 °F | 25.4 °F | 0.8 in. |
| March | 19.6 °F | 38.0 °F | 1.44 in. |
| April | 33.0 °F | 53.9 °F | 2.56 in. |
| May | 46.1 °F | 67.6 °F | 3.42 in. |
| June | 57.1 °F | 77.1 °F | 4.77 in. |
| July | 61.1 °F | 81.1 °F | 3.95 in. |
| August | 58.1 °F | 78.9 °F | 4.12 in. |
| September | 49.5 °F | 72.1 °F | 2.95 in. |
| October | 36.4 °F | 57.1 °F | 2.45 in. |
| November | 23.1 °F | 40.2 °F | 1.29 in. |
| December | 10.4 °F | 26.3 °F | 0.95 in. |
| Annual | 33.7 °F | 53.2 °F | 29.41 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 4b : -25°F to -20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |