Merrill, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 37.3 °F (low) to 57.3 °F (high). Annual precipitation averages 33.6 Inches. Merrill is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.8 °F | 29.8 °F | 2.14 in. |
| February | 14.9 °F | 32.2 °F | 1.75 in. |
| March | 23.3 °F | 42.7 °F | 1.98 in. |
| April | 34.4 °F | 56.1 °F | 3.44 in. |
| May | 46.4 °F | 68.8 °F | 3.66 in. |
| June | 56.2 °F | 78.5 °F | 3.52 in. |
| July | 59.4 °F | 82.5 °F | 3.13 in. |
| August | 57.4 °F | 80.4 °F | 3.49 in. |
| September | 49.5 °F | 74.1 °F | 2.77 in. |
| October | 39.3 °F | 60.9 °F | 3.17 in. |
| November | 30.1 °F | 46.8 °F | 2.51 in. |
| December | 21.6 °F | 35.1 °F | 2.02 in. |
| Annual | 37.3 °F | 57.3 °F | 33.58 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |