Grasonville, Maryland has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.6 °C (low) to 18.7 °C (high). Annual precipitation averages 1149.4 Millimeters. Grasonville is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -1.9 °C | 6.3 °C | 82.04 mm |
| February | -1.3 °C | 7.6 °C | 70.36 mm |
| March | 2.5 °C | 11.8 °C | 103.63 mm |
| April | 8.1 °C | 18.3 °C | 87.12 mm |
| May | 13.5 °C | 23.2 °C | 103.38 mm |
| June | 18.8 °C | 28.1 °C | 108.46 mm |
| July | 21.7 °C | 30.6 °C | 109.73 mm |
| August | 20.7 °C | 29.6 °C | 107.44 mm |
| September | 17.2 °C | 26.1 °C | 107.95 mm |
| October | 10.7 °C | 19.9 °C | 97.79 mm |
| November | 5 °C | 13.7 °C | 77.47 mm |
| December | 0.7 °C | 8.6 °C | 93.98 mm |
| Annual | 9.6 °C | 18.7 °C | 1149.35 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |