Allen, Maryland has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.3 °C (low) to 20 °C (high). Annual precipitation averages 1179.6 Millimeters. Allen is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.4 °C | 8.1 °C | 87.12 mm |
| February | -1.9 °C | 9.4 °C | 75.18 mm |
| March | 1.6 °C | 13.4 °C | 103.89 mm |
| April | 6.8 °C | 19.8 °C | 89.66 mm |
| May | 12 °C | 24.4 °C | 91.69 mm |
| June | 17.2 °C | 28.9 °C | 102.62 mm |
| July | 20 °C | 31.4 °C | 112.01 mm |
| August | 18.7 °C | 30.2 °C | 127.25 mm |
| September | 15.4 °C | 27.3 °C | 112.78 mm |
| October | 8.9 °C | 21.6 °C | 102.62 mm |
| November | 3.3 °C | 15.4 °C | 80.77 mm |
| December | -0.3 °C | 10.4 °C | 93.98 mm |
| Annual | 8.3 °C | 20 °C | 1179.57 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |