Preston, Maryland has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.4 °C (low) to 19.4 °C (high). Annual precipitation averages 1142 Millimeters. Preston is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.6 °C | 6.9 °C | 85.09 mm |
| February | -2 °C | 8.4 °C | 72.14 mm |
| March | 1.6 °C | 12.7 °C | 103.12 mm |
| April | 7.1 °C | 19.2 °C | 89.92 mm |
| May | 12.4 °C | 24 °C | 94.49 mm |
| June | 17.6 °C | 28.9 °C | 106.43 mm |
| July | 20.2 °C | 31.3 °C | 104.65 mm |
| August | 18.9 °C | 30.1 °C | 116.59 mm |
| September | 15.4 °C | 26.9 °C | 96.27 mm |
| October | 9.3 °C | 20.9 °C | 98.81 mm |
| November | 3.6 °C | 14.6 °C | 79.25 mm |
| December | -0.2 °C | 9.4 °C | 95.25 mm |
| Annual | 8.4 °C | 19.4 °C | 1142.01 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| 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 | Extreme Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |