Napoleon, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 38.3 °F (low) to 58.2 °F (high). Annual precipitation averages 35.6 Inches. Napoleon 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 | 15.8 °F | 31.0 °F | 2.35 in. |
| February | 16.7 °F | 34.1 °F | 1.98 in. |
| March | 24.9 °F | 44.3 °F | 2.33 in. |
| April | 36.0 °F | 57.7 °F | 3.29 in. |
| May | 47.4 °F | 69.5 °F | 3.92 in. |
| June | 56.8 °F | 78.8 °F | 3.69 in. |
| July | 60.2 °F | 82.6 °F | 3.43 in. |
| August | 58.6 °F | 80.7 °F | 3.53 in. |
| September | 51.0 °F | 74.5 °F | 3.13 in. |
| October | 40.0 °F | 61.4 °F | 3.0 in. |
| November | 30.3 °F | 47.6 °F | 2.73 in. |
| December | 22.2 °F | 36.0 °F | 2.24 in. |
| Annual | 38.3 °F | 58.2 °F | 35.62 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 |