| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F | |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°F | |
| 1990 Hardiness Zone: | Zone 1b: -15F to -10F | |
| Average First Frost Date: | Oct. 1 - Oct. 10 | |
| Average Last Frost Date: | May 11 - May 20 | |
| Koppen-Geiger Climate Zone: | Dfb - Humid Continental Mild Summer, Wet All Year | |
| Ecoregion: | 59f - Gulf of Maine Coastal Lowland | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 03801 - Portsmouth, NH | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 14 | 16 | 25 | 34 | 43 | 53 | 59 | 57 | 50 | 39 | 30 | 20 | 37 |
| Avg Max Temp (°F) | 33 | 36 | 44 | 55 | 67 | 76 | 81 | 79 | 72 | 61 | 48 | 37 | 57 |
| Avg Precip (In.) | 4.12 | 3.34 | 4.2 | 4.32 | 3.62 | 3.59 | 3.45 | 3.42 | 3.81 | 4.32 | 4.75 | 4.33 | 47.26 |