Hopatcong, New Jersey has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 5.2 °C (low) to 15.4 °C (high). Annual precipitation averages 1288.3 Millimeters. Hopatcong is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.2 °C | 1.8 °C | 94.74 mm |
| February | -6.7 °C | 3.1 °C | 79.76 mm |
| March | -2.3 °C | 7.7 °C | 107.44 mm |
| April | 3.9 °C | 14.9 °C | 98.81 mm |
| May | 9.4 °C | 20.6 °C | 102.11 mm |
| June | 15.2 °C | 25.8 °C | 130.56 mm |
| July | 17.1 °C | 28.5 °C | 112.27 mm |
| August | 16.8 °C | 27.3 °C | 121.41 mm |
| September | 12.4 °C | 23.4 °C | 122.43 mm |
| October | 6.4 °C | 16.7 °C | 113.03 mm |
| November | 0.9 °C | 10.5 °C | 90.17 mm |
| December | -3.4 °C | 4.5 °C | 115.57 mm |
| Annual | 5.2 °C | 15.4 °C | 1288.3 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |