Rockland, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.5 °C (low) to 12 °C (high). Annual precipitation averages 1309.7 Millimeters. Rockland is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.3 °C | -0.2 °C | 115.57 mm |
| February | -7.6 °C | 0.8 °C | 96.27 mm |
| March | -3.9 °C | 4.4 °C | 121.67 mm |
| April | 1.4 °C | 10.2 °C | 120.4 mm |
| May | 6.4 °C | 15.6 °C | 95.76 mm |
| June | 11.2 °C | 20.5 °C | 102.11 mm |
| July | 14.5 °C | 23.8 °C | 82.3 mm |
| August | 14.3 °C | 23.7 °C | 75.95 mm |
| September | 11.2 °C | 20.1 °C | 113.79 mm |
| October | 6.1 °C | 13.9 °C | 134.11 mm |
| November | 1.3 °C | 8.6 °C | 124.97 mm |
| December | -4.3 °C | 3.1 °C | 126.75 mm |
| Annual | 3.5 °C | 12 °C | 1309.65 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |