Charlestown, Maryland has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 45.6 °F (low) to 64.7 °F (high). Annual precipitation averages 47.9 Inches. Charlestown is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 24.8 °F | 41.9 °F | 3.43 in. |
| February | 25.7 °F | 44.4 °F | 2.89 in. |
| March | 32.6 °F | 52.5 °F | 4.28 in. |
| April | 43.3 °F | 63.5 °F | 3.8 in. |
| May | 52.9 °F | 73.2 °F | 3.89 in. |
| June | 62.3 °F | 82.1 °F | 4.64 in. |
| July | 67.5 °F | 86.5 °F | 4.57 in. |
| August | 65.9 °F | 85.0 °F | 4.23 in. |
| September | 59.0 °F | 78.5 °F | 4.52 in. |
| October | 46.8 °F | 66.8 °F | 4.2 in. |
| November | 37.0 °F | 55.7 °F | 3.28 in. |
| December | 29.9 °F | 46.0 °F | 4.17 in. |
| Annual | 45.6 °F | 64.7 °F | 47.9 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : 5°F to 10°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |