Grantsville, Maryland has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3 °C (low) to 14.5 °C (high). Annual precipitation averages 1182.1 Millimeters. 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 | -8.3 °C | 1.1 °C | 90.68 mm |
| February | -7.4 °C | 2.9 °C | 83.82 mm |
| March | -3.8 °C | 7.7 °C | 101.09 mm |
| April | 1.6 °C | 15.3 °C | 105.41 mm |
| May | 7.4 °C | 20.2 °C | 126.75 mm |
| June | 12.1 °C | 24.2 °C | 124.21 mm |
| July | 14.2 °C | 26.2 °C | 108.71 mm |
| August | 13.4 °C | 25.5 °C | 95.5 mm |
| September | 9.6 °C | 22.1 °C | 94.23 mm |
| October | 3.7 °C | 15.8 °C | 81.28 mm |
| November | -1.7 °C | 9.1 °C | 77.72 mm |
| December | -5.3 °C | 3.4 °C | 92.71 mm |
| Annual | 3 °C | 14.5 °C | 1182.11 mm |
| 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 : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |