Grahamtown, Maryland has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.4 °C (low) to 15.4 °C (high). Annual precipitation averages 1117.1 Millimeters. Grahamtown is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.8 °C | 1.6 °C | 76.96 mm |
| February | -6.2 °C | 3.5 °C | 75.18 mm |
| March | -2.4 °C | 8.3 °C | 101.6 mm |
| April | 3.2 °C | 16.3 °C | 102.87 mm |
| May | 8.9 °C | 21.1 °C | 119.63 mm |
| June | 13.4 °C | 25.3 °C | 116.59 mm |
| July | 15.7 °C | 27.6 °C | 94.49 mm |
| August | 14.8 °C | 26.8 °C | 83.57 mm |
| September | 11.1 °C | 23.3 °C | 97.03 mm |
| October | 5.2 °C | 16.9 °C | 84.84 mm |
| November | -0.1 °C | 9.8 °C | 77.72 mm |
| December | -4.1 °C | 4 °C | 86.61 mm |
| Annual | 4.4 °C | 15.4 °C | 1117.09 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |