Hillsboro, Maryland has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.8 °C (low) to 19.2 °C (high). Annual precipitation averages 1182.6 Millimeters. Hillsboro 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 | -3.2 °C | 6.7 °C | 87.38 mm |
| February | -2.7 °C | 8.1 °C | 75.69 mm |
| March | 1.1 °C | 12.4 °C | 102.36 mm |
| April | 6.6 °C | 18.9 °C | 92.71 mm |
| May | 11.9 °C | 23.8 °C | 102.36 mm |
| June | 17 °C | 28.8 °C | 110.74 mm |
| July | 19.7 °C | 31.2 °C | 111.51 mm |
| August | 18.5 °C | 30.1 °C | 117.35 mm |
| September | 14.8 °C | 26.8 °C | 103.38 mm |
| October | 8.4 °C | 20.6 °C | 100.84 mm |
| November | 2.8 °C | 14.4 °C | 82.04 mm |
| December | -0.8 °C | 9.1 °C | 96.27 mm |
| Annual | 7.8 °C | 19.2 °C | 1182.63 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 7a : -17.8°C to -15°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |