Williston, Maryland has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 46 °F (low) to 66.7 °F (high). Annual precipitation averages 46.2 Inches. Williston 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 | 26.0 °F | 44.1 °F | 3.39 in. |
| February | 27.2 °F | 46.8 °F | 2.96 in. |
| March | 33.7 °F | 54.4 °F | 3.98 in. |
| April | 43.7 °F | 66.2 °F | 3.64 in. |
| May | 53.4 °F | 75.1 °F | 3.97 in. |
| June | 62.5 °F | 83.8 °F | 4.33 in. |
| July | 67.3 °F | 88.2 °F | 4.35 in. |
| August | 65.1 °F | 86.0 °F | 4.66 in. |
| September | 58.7 °F | 80.3 °F | 4.03 in. |
| October | 47.2 °F | 69.3 °F | 3.96 in. |
| November | 36.9 °F | 58.0 °F | 3.22 in. |
| December | 30.4 °F | 48.5 °F | 3.7 in. |
| Annual | 46 °F | 66.7 °F | 46.19 in. |
| 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 : 5°F to 10°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |