Duluth, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 32.4 °F (low) to 49.2 °F (high). Annual precipitation averages 30 Inches. Duluth 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 | 4.5 °F | 21.2 °F | 1.08 in. |
| February | 7.3 °F | 25.7 °F | 1.01 in. |
| March | 18.4 °F | 35.7 °F | 1.28 in. |
| April | 30.5 °F | 46.4 °F | 2.53 in. |
| May | 39.9 °F | 58.6 °F | 3.05 in. |
| June | 49.2 °F | 67.8 °F | 4.16 in. |
| July | 57.3 °F | 75.6 °F | 3.82 in. |
| August | 57.3 °F | 74.8 °F | 3.49 in. |
| September | 49.1 °F | 66.5 °F | 3.27 in. |
| October | 37.9 °F | 53.0 °F | 3.04 in. |
| November | 25.2 °F | 38.9 °F | 1.91 in. |
| December | 12.3 °F | 26.3 °F | 1.36 in. |
| Annual | 32.4 °F | 49.2 °F | 30 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 | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |