Allegan, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 38.7 °F (low) to 58.2 °F (high). Annual precipitation averages 42 Inches. Allegan is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.9 °F | 31.7 °F | 3.56 in. |
| February | 18.0 °F | 34.0 °F | 2.33 in. |
| March | 25.3 °F | 44.4 °F | 2.53 in. |
| April | 35.5 °F | 57.8 °F | 4.03 in. |
| May | 46.5 °F | 69.2 °F | 4.48 in. |
| June | 55.6 °F | 78.3 °F | 4.09 in. |
| July | 59.4 °F | 82.2 °F | 3.78 in. |
| August | 58.5 °F | 80.7 °F | 3.69 in. |
| September | 51.1 °F | 74.5 °F | 3.37 in. |
| October | 40.6 °F | 61.3 °F | 3.95 in. |
| November | 31.6 °F | 47.8 °F | 3.25 in. |
| December | 24.0 °F | 36.6 °F | 2.96 in. |
| Annual | 38.7 °F | 58.2 °F | 42.02 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| 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 |