Rockville, Maryland has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.8 °C (low) to 18.4 °C (high). Annual precipitation averages 1142.5 Millimeters. Rockville is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.5 °C | 5.7 °C | 78.74 mm |
| February | -2.7 °C | 7.4 °C | 69.6 mm |
| March | 1.1 °C | 12.1 °C | 100.08 mm |
| April | 6.6 °C | 18.8 °C | 86.11 mm |
| May | 12.1 °C | 23.3 °C | 112.78 mm |
| June | 16.9 °C | 28 °C | 113.03 mm |
| July | 19.6 °C | 30.4 °C | 108.71 mm |
| August | 18.6 °C | 29.3 °C | 89.66 mm |
| September | 14.9 °C | 25.6 °C | 111.76 mm |
| October | 8.3 °C | 19.3 °C | 97.28 mm |
| November | 2.8 °C | 13.3 °C | 82.3 mm |
| December | -1.1 °C | 7.9 °C | 92.46 mm |
| Annual | 7.8 °C | 18.4 °C | 1142.51 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |