Antietam, Maryland has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.8 °F (low) to 65.7 °F (high). Annual precipitation averages 42.5 Inches. Antietam is located in USDA Plant Hardiness Zone 7a. 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 | 22.2 °F | 41.5 °F | 3.04 in. |
| February | 23.7 °F | 45.1 °F | 2.42 in. |
| March | 30.3 °F | 53.9 °F | 3.62 in. |
| April | 41.1 °F | 66.4 °F | 3.46 in. |
| May | 51.3 °F | 75.1 °F | 4.4 in. |
| June | 59.6 °F | 83.4 °F | 3.91 in. |
| July | 64.3 °F | 87.9 °F | 4.04 in. |
| August | 62.6 °F | 86.1 °F | 3.33 in. |
| September | 55.6 °F | 79.6 °F | 4.32 in. |
| October | 42.6 °F | 68.2 °F | 3.45 in. |
| November | 33.3 °F | 56.1 °F | 3.1 in. |
| December | 26.9 °F | 45.3 °F | 3.44 in. |
| Annual | 42.8 °F | 65.7 °F | 42.53 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |