Erma, New Jersey has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.4 °C (low) to 17.3 °C (high). Annual precipitation averages 1134.6 Millimeters. Erma 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 | -1.8 °C | 6.1 °C | 82.55 mm |
| February | -1.4 °C | 6.7 °C | 72.64 mm |
| March | 2.3 °C | 10.2 °C | 110.24 mm |
| April | 7.6 °C | 15.3 °C | 88.39 mm |
| May | 12.6 °C | 20.5 °C | 91.19 mm |
| June | 18 °C | 25.6 °C | 89.15 mm |
| July | 20.9 °C | 28.6 °C | 106.43 mm |
| August | 20.3 °C | 27.9 °C | 103.89 mm |
| September | 17.2 °C | 25 °C | 91.19 mm |
| October | 11.1 °C | 19.2 °C | 109.73 mm |
| November | 5.1 °C | 13.4 °C | 83.82 mm |
| December | 0.9 °C | 8.7 °C | 105.41 mm |
| Annual | 9.4 °C | 17.3 °C | 1134.63 mm |
| 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 : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |