Dennison, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 35.2 °F (low) to 54.7 °F (high). Annual precipitation averages 33.7 Inches. Dennison is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 5.9 °F | 23.2 °F | 0.9 in. |
| February | 9.4 °F | 28.0 °F | 0.99 in. |
| March | 21.8 °F | 40.3 °F | 1.82 in. |
| April | 34.4 °F | 55.7 °F | 2.91 in. |
| May | 47.0 °F | 68.1 °F | 4.39 in. |
| June | 57.6 °F | 77.7 °F | 5.22 in. |
| July | 61.2 °F | 81.4 °F | 4.08 in. |
| August | 58.7 °F | 79.6 °F | 4.62 in. |
| September | 50.4 °F | 72.7 °F | 3.42 in. |
| October | 37.5 °F | 58.7 °F | 2.47 in. |
| November | 25.4 °F | 42.3 °F | 1.68 in. |
| December | 13.0 °F | 28.8 °F | 1.23 in. |
| Annual | 35.2 °F | 54.7 °F | 33.73 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 |