| 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 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: | 82g - Downeast Coast |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 04421 - Castine, ME | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 11 | 13 | 23 | 33 | 43 | 52 | 57 | 56 | 48 | 39 | 31 | 18 | 35 |
| Avg Max Temp (°F) | 31 | 34 | 42 | 53 | 65 | 74 | 80 | 78 | 70 | 58 | 47 | 36 | 56 |
| Avg Precip (In.) | 4.14 | 3.12 | 4.3 | 4.29 | 4.04 | 3.73 | 3.28 | 2.97 | 4 | 4.21 | 4.71 | 4.26 | 47.05 |