Smyrna, Delaware has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.8 °C (low) to 18.3 °C (high). Annual precipitation averages 1174.3 Millimeters. Smyrna 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 | -3.8 °C | 5.8 °C | 84.84 mm |
| February | -3.2 °C | 6.9 °C | 74.93 mm |
| March | 0.8 °C | 11.3 °C | 105.41 mm |
| April | 6.6 °C | 17.8 °C | 91.69 mm |
| May | 11.9 °C | 22.8 °C | 98.81 mm |
| June | 17 °C | 27.8 °C | 114.81 mm |
| July | 19.8 °C | 30.3 °C | 110.24 mm |
| August | 18.8 °C | 29.2 °C | 111.25 mm |
| September | 15.1 °C | 25.9 °C | 105.66 mm |
| October | 8.6 °C | 19.8 °C | 97.54 mm |
| November | 2.7 °C | 13.7 °C | 80.26 mm |
| December | -1.1 °C | 8.3 °C | 98.81 mm |
| Annual | 7.8 °C | 18.3 °C | 1174.25 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 | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |