| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°F | |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 6b: -5°F to 0°F | |
| 1990 Hardiness Zone: | Zone 6a: -10F to -5F | |
| Average First Frost Date: | Oct. 11 - Oct. 20 | |
| Average Last Frost Date: | May 1 - May 10 | |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers | |
| Ecoregion: | 59a - Connecticut Valley | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 06480 - Portland, CT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 19 | 21 | 29 | 38 | 48 | 57 | 63 | 61 | 53 | 42 | 34 | 25 | 41 |
| Avg Max Temp (°F) | 36 | 39 | 47 | 59 | 70 | 79 | 84 | 81 | 73 | 62 | 51 | 40 | 60 |
| Avg Precip (In.) | 4.23 | 3.13 | 4.24 | 4.33 | 4.25 | 4.14 | 4.05 | 4.26 | 4.24 | 4.33 | 4.19 | 3.92 | 49.31 |