Decatur, Michigan has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.5 °F (low) to 58.2 °F (high). Annual precipitation averages 39.8 Inches. Decatur 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.2 °F | 31.2 °F | 2.86 in. |
| February | 18.6 °F | 34.1 °F | 2.15 in. |
| March | 26.3 °F | 44.7 °F | 2.36 in. |
| April | 37.0 °F | 57.5 °F | 3.5 in. |
| May | 48.3 °F | 69.0 °F | 4.15 in. |
| June | 57.3 °F | 78.4 °F | 3.95 in. |
| July | 61.0 °F | 82.6 °F | 3.75 in. |
| August | 59.6 °F | 80.9 °F | 4.03 in. |
| September | 52.0 °F | 74.6 °F | 3.45 in. |
| October | 40.9 °F | 61.3 °F | 4.02 in. |
| November | 31.8 °F | 47.7 °F | 2.98 in. |
| December | 23.4 °F | 36.1 °F | 2.59 in. |
| Annual | 39.5 °F | 58.2 °F | 39.79 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| 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 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |