Portland, Michigan has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.5 °C (low) to 14.1 °C (high). Annual precipitation averages 911.9 Millimeters. 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 | -8.9 °C | -1.1 °C | 59.18 mm |
| February | -8.2 °C | 0.7 °C | 55.12 mm |
| March | -3.8 °C | 6.5 °C | 56.39 mm |
| April | 1.7 °C | 13.9 °C | 88.14 mm |
| May | 8.4 °C | 20.6 °C | 100.08 mm |
| June | 13.8 °C | 25.7 °C | 93.22 mm |
| July | 15.8 °C | 27.8 °C | 83.82 mm |
| August | 14.9 °C | 26.7 °C | 90.93 mm |
| September | 10.3 °C | 22.8 °C | 75.69 mm |
| October | 4.4 °C | 15.7 °C | 85.09 mm |
| November | -0.6 °C | 8.2 °C | 69.09 mm |
| December | -5.3 °C | 1.8 °C | 55.12 mm |
| Annual | 3.5 °C | 14.1 °C | 911.87 mm |
| 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 : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |