Grantsville, Maryland has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 37.3 °F (low) to 58 °F (high). Annual precipitation averages 46.5 Inches. Grantsville is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.1 °F | 34.0 °F | 3.57 in. |
| February | 18.7 °F | 37.3 °F | 3.3 in. |
| March | 25.1 °F | 45.8 °F | 3.98 in. |
| April | 34.9 °F | 59.6 °F | 4.15 in. |
| May | 45.4 °F | 68.3 °F | 4.99 in. |
| June | 53.8 °F | 75.6 °F | 4.89 in. |
| July | 57.6 °F | 79.2 °F | 4.28 in. |
| August | 56.1 °F | 77.9 °F | 3.76 in. |
| September | 49.2 °F | 71.8 °F | 3.71 in. |
| October | 38.6 °F | 60.5 °F | 3.2 in. |
| November | 29.0 °F | 48.3 °F | 3.06 in. |
| December | 22.4 °F | 38.2 °F | 3.65 in. |
| Annual | 37.3 °F | 58 °F | 46.54 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |