| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°F | |
| 2012 Hardiness Zone: | Zone 5b: -15°F to -10°F | |
| 1990 Hardiness Zone: | Zone 5a: -20F to -15F | |
| Average First Frost Date: | Oct. 11 - Oct. 20 | |
| 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 04103 - Portland, ME | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 12 | 15 | 25 | 34 | 44 | 53 | 58 | 57 | 49 | 38 | 30 | 18 | 36 |
| Avg Max Temp (°F) | 31 | 34 | 43 | 54 | 65 | 74 | 80 | 78 | 70 | 59 | 47 | 36 | 56 |
| Avg Precip (In.) | 4.06 | 3.14 | 4.15 | 4.26 | 3.81 | 3.36 | 3.34 | 3.07 | 3.42 | 4.32 | 4.71 | 4.23 | 45.86 |