Portland, Michigan has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38.4 °F (low) to 57.4 °F (high). Annual precipitation averages 35.9 Inches. Portland 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 | 16.0 °F | 30.0 °F | 2.33 in. |
| February | 17.2 °F | 33.2 °F | 2.17 in. |
| March | 25.1 °F | 43.7 °F | 2.22 in. |
| April | 35.0 °F | 57.0 °F | 3.47 in. |
| May | 47.1 °F | 69.1 °F | 3.94 in. |
| June | 56.9 °F | 78.3 °F | 3.67 in. |
| July | 60.5 °F | 82.0 °F | 3.3 in. |
| August | 58.9 °F | 80.0 °F | 3.58 in. |
| September | 50.5 °F | 73.1 °F | 2.98 in. |
| October | 39.9 °F | 60.3 °F | 3.35 in. |
| November | 30.9 °F | 46.7 °F | 2.72 in. |
| December | 22.5 °F | 35.2 °F | 2.17 in. |
| Annual | 38.4 °F | 57.4 °F | 35.9 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 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |