Mountain Lakes, New Jersey has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 5.6 °C (low) to 16.5 °C (high). Annual precipitation averages 1259.6 Millimeters. Mountain Lakes is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.3 °C | 3.1 °C | 94.74 mm |
| February | -5.8 °C | 4.4 °C | 70.36 mm |
| March | -1.6 °C | 8.9 °C | 104.9 mm |
| April | 4.4 °C | 15.9 °C | 101.35 mm |
| May | 9.7 °C | 21.5 °C | 103.12 mm |
| June | 15.1 °C | 26.3 °C | 129.29 mm |
| July | 17.7 °C | 29.6 °C | 112.27 mm |
| August | 16.9 °C | 28.4 °C | 117.86 mm |
| September | 12.7 °C | 24.7 °C | 111.76 mm |
| October | 6.3 °C | 18 °C | 112.01 mm |
| November | 1.2 °C | 11.6 °C | 91.95 mm |
| December | -2.9 °C | 5.8 °C | 109.98 mm |
| Annual | 5.6 °C | 16.5 °C | 1259.59 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |