Mount Royal, New Jersey has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.6 °C (low) to 18.2 °C (high). Annual precipitation averages 1189.8 Millimeters. Mount Royal is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.1 °C | 5.2 °C | 91.95 mm |
| February | -2.3 °C | 6.6 °C | 72.14 mm |
| March | 1.3 °C | 10.9 °C | 112.27 mm |
| April | 7.1 °C | 17.7 °C | 89.92 mm |
| May | 12.4 °C | 23 °C | 93.98 mm |
| June | 17.8 °C | 28.2 °C | 107.95 mm |
| July | 20.8 °C | 30.6 °C | 116.84 mm |
| August | 20 °C | 29.5 °C | 117.35 mm |
| September | 16.2 °C | 25.8 °C | 105.16 mm |
| October | 9.5 °C | 19.3 °C | 98.3 mm |
| November | 3.8 °C | 13.2 °C | 77.47 mm |
| December | -0.1 °C | 7.9 °C | 106.43 mm |
| Annual | 8.6 °C | 18.2 °C | 1189.76 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |