Portsmouth, Virginia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.5 °C (low) to 21.1 °C (high). Annual precipitation averages 1283.2 Millimeters. Portsmouth 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. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.8 °C | 10.4 °C | 90.42 mm |
| February | 1.5 °C | 11.8 °C | 71.88 mm |
| March | 5.1 °C | 15.4 °C | 100.84 mm |
| April | 10.2 °C | 20.8 °C | 91.69 mm |
| May | 15.1 °C | 24.9 °C | 107.44 mm |
| June | 19.8 °C | 29 °C | 121.67 mm |
| July | 22.3 °C | 31.4 °C | 136.14 mm |
| August | 21.6 °C | 30.3 °C | 144.27 mm |
| September | 18.9 °C | 27.3 °C | 136.65 mm |
| October | 12.6 °C | 22.1 °C | 105.66 mm |
| November | 6.6 °C | 16.8 °C | 85.6 mm |
| December | 3 °C | 12.5 °C | 90.93 mm |
| Annual | 11.5 °C | 21.1 °C | 1283.19 mm |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 30-40 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 | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |