Deal Island, Maryland has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 51.6 °F (low) to 65.5 °F (high). Annual precipitation averages 45.7 Inches. Deal Island 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 Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 30.9 °F | 44.3 °F | 3.3 in. |
| February | 32.0 °F | 46.5 °F | 2.93 in. |
| March | 38.4 °F | 53.4 °F | 4.12 in. |
| April | 48.6 °F | 64.6 °F | 3.43 in. |
| May | 58.5 °F | 72.9 °F | 3.66 in. |
| June | 67.6 °F | 81.4 °F | 4.06 in. |
| July | 72.9 °F | 85.6 °F | 4.42 in. |
| August | 71.4 °F | 83.8 °F | 4.71 in. |
| September | 65.4 °F | 78.5 °F | 4.28 in. |
| October | 54.2 °F | 68.1 °F | 4.05 in. |
| November | 43.2 °F | 57.4 °F | 3.13 in. |
| December | 35.8 °F | 49.0 °F | 3.65 in. |
| Annual | 51.6 °F | 65.5 °F | 45.74 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 50-75 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 |