Arnold, Maryland has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 49.2 °F (low) to 65.7 °F (high). Annual precipitation averages 45.5 Inches. Arnold is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 27.8 °F | 44.0 °F | 3.15 in. |
| February | 29.0 °F | 46.1 °F | 2.72 in. |
| March | 35.9 °F | 53.7 °F | 4.22 in. |
| April | 46.5 °F | 64.5 °F | 3.45 in. |
| May | 56.2 °F | 73.4 °F | 4.17 in. |
| June | 65.9 °F | 82.5 °F | 4.4 in. |
| July | 71.0 °F | 86.9 °F | 4.31 in. |
| August | 69.7 °F | 85.1 °F | 4.0 in. |
| September | 63.3 °F | 78.7 °F | 4.42 in. |
| October | 51.5 °F | 67.7 °F | 3.83 in. |
| November | 40.8 °F | 57.1 °F | 3.07 in. |
| December | 32.7 °F | 48.1 °F | 3.78 in. |
| Annual | 49.2 °F | 65.7 °F | 45.52 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 8a : 10°F to 15°F |
| Plant Hardiness Zone - 2012 | Zone 7b : 5°F to 10°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |