Grantsburg, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 31.4 °F (low) to 53.8 °F (high). Annual precipitation averages 32.4 Inches. Grantsburg is located in USDA Plant Hardiness Zone 4a. 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 | 1.3 °F | 22.0 °F | 0.78 in. |
| February | 4.7 °F | 27.5 °F | 0.84 in. |
| March | 17.6 °F | 40.2 °F | 1.54 in. |
| April | 30.4 °F | 54.6 °F | 2.79 in. |
| May | 43.0 °F | 68.0 °F | 4.1 in. |
| June | 53.3 °F | 77.1 °F | 4.73 in. |
| July | 57.7 °F | 81.5 °F | 4.5 in. |
| August | 55.2 °F | 79.5 °F | 4.11 in. |
| September | 46.9 °F | 71.4 °F | 3.27 in. |
| October | 35.0 °F | 56.9 °F | 2.99 in. |
| November | 22.5 °F | 40.3 °F | 1.62 in. |
| December | 9.6 °F | 27.0 °F | 1.15 in. |
| Annual | 31.4 °F | 53.8 °F | 32.42 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 4a : -30°F to -25°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |