Garretts Mill, Maryland has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 43.7 °F (low) to 65.2 °F (high). Annual precipitation averages 42.5 Inches. Garretts Mill is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 23.7 °F | 41.3 °F | 3.14 in. |
| February | 25.1 °F | 44.8 °F | 2.41 in. |
| March | 31.9 °F | 53.3 °F | 3.58 in. |
| April | 41.8 °F | 65.5 °F | 3.39 in. |
| May | 51.5 °F | 74.4 °F | 4.29 in. |
| June | 60.4 °F | 82.6 °F | 3.93 in. |
| July | 64.8 °F | 87.2 °F | 4.07 in. |
| August | 62.9 °F | 85.4 °F | 3.3 in. |
| September | 55.9 °F | 78.7 °F | 4.42 in. |
| October | 44.5 °F | 67.6 °F | 3.4 in. |
| November | 34.5 °F | 55.8 °F | 3.12 in. |
| December | 27.5 °F | 45.3 °F | 3.41 in. |
| Annual | 43.7 °F | 65.2 °F | 42.46 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |