National, Maryland has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.5 °C (low) to 15.7 °C (high). Annual precipitation averages 1120.6 Millimeters. National 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 | -6.6 °C | 1.9 °C | 78.74 mm |
| February | -5.9 °C | 3.8 °C | 74.42 mm |
| March | -2.3 °C | 8.7 °C | 100.08 mm |
| April | 3.3 °C | 16.6 °C | 101.85 mm |
| May | 8.8 °C | 21.4 °C | 121.92 mm |
| June | 13.5 °C | 25.6 °C | 116.08 mm |
| July | 15.8 °C | 27.8 °C | 95.5 mm |
| August | 14.9 °C | 27.1 °C | 86.87 mm |
| September | 11.2 °C | 23.6 °C | 99.31 mm |
| October | 5.3 °C | 17.2 °C | 83.31 mm |
| November | 0 °C | 10 °C | 76.71 mm |
| December | -3.9 °C | 4.3 °C | 85.85 mm |
| Annual | 4.5 °C | 15.7 °C | 1120.64 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 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |