Middletown, Delaware has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.6 °C (low) to 18.2 °C (high). Annual precipitation averages 1139.5 Millimeters. Middletown 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 | -4 °C | 5.6 °C | 78.49 mm |
| February | -3.4 °C | 6.9 °C | 68.58 mm |
| March | 0.5 °C | 11.4 °C | 102.36 mm |
| April | 6.2 °C | 17.8 °C | 90.42 mm |
| May | 11.6 °C | 22.9 °C | 95.76 mm |
| June | 16.8 °C | 27.7 °C | 116.08 mm |
| July | 19.7 °C | 30.2 °C | 107.95 mm |
| August | 18.8 °C | 29.2 °C | 98.55 mm |
| September | 15.1 °C | 25.8 °C | 107.19 mm |
| October | 8.4 °C | 19.5 °C | 98.81 mm |
| November | 2.6 °C | 13.4 °C | 76.96 mm |
| December | -1.2 °C | 7.9 °C | 98.3 mm |
| Annual | 7.6 °C | 18.2 °C | 1139.45 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 | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |