| 2023 Hardiness Zone: | Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 5a: -20°F to -15°F 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: | 82f - Midcoast |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 04862 - Union, ME | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 11 | 13 | 23 | 33 | 43 | 53 | 58 | 57 | 50 | 39 | 30 | 18 | 36 |
| Avg Max Temp (°F) | 30 | 32 | 41 | 52 | 64 | 72 | 78 | 77 | 68 | 57 | 46 | 35 | 54 |
| Avg Precip (In.) | 4.19 | 3.31 | 4.35 | 4.19 | 3.93 | 3.64 | 3.34 | 2.92 | 3.93 | 4.13 | 4.8 | 4.27 | 47 |