Portland, Arkansas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.7 °C (low) to 23.8 °C (high). Annual precipitation averages 1456.2 Millimeters. Portland is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.9 °C | 12.1 °C | 147.32 mm |
| February | 2.7 °C | 14.6 °C | 143.26 mm |
| March | 6.9 °C | 19.2 °C | 138.43 mm |
| April | 11.7 °C | 24.1 °C | 149.61 mm |
| May | 16.7 °C | 28.4 °C | 127.25 mm |
| June | 20.8 °C | 32.2 °C | 90.17 mm |
| July | 22.4 °C | 33.4 °C | 108.2 mm |
| August | 21.6 °C | 33.5 °C | 105.66 mm |
| September | 17.8 °C | 31.1 °C | 87.88 mm |
| October | 11.2 °C | 25.5 °C | 108.97 mm |
| November | 5.7 °C | 18.6 °C | 107.19 mm |
| December | 2.5 °C | 13.4 °C | 142.24 mm |
| Annual | 11.7 °C | 23.8 °C | 1456.18 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |