| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F | |
| 2012 Hardiness Zone: | Zone 5b: -15°F to -10°F | |
| 1990 Hardiness Zone: | Zone 1b: -15F to -10F | |
| 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 04101 - 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 | 59 | 57 | 49 | 38 | 30 | 19 | 36 |
| Avg Max Temp (°F) | 31 | 34 | 42 | 53 | 64 | 74 | 79 | 78 | 69 | 58 | 47 | 36 | 56 |
| Avg Precip (In.) | 4.08 | 3.15 | 4.14 | 4.26 | 3.81 | 3.33 | 3.33 | 3.06 | 3.41 | 4.33 | 4.71 | 4.24 | 45.85 |