Smithville, New Jersey has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.8 °C (low) to 17.6 °C (high). Annual precipitation averages 1203 Millimeters. Smithville 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. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.8 °C | 5.7 °C | 93.22 mm |
| February | -3.1 °C | 6.8 °C | 77.22 mm |
| March | 0.3 °C | 10.3 °C | 119.38 mm |
| April | 5.7 °C | 16.3 °C | 90.17 mm |
| May | 11.1 °C | 21.3 °C | 88.14 mm |
| June | 16.6 °C | 26.6 °C | 96.01 mm |
| July | 19.6 °C | 29.2 °C | 117.6 mm |
| August | 19.1 °C | 28.4 °C | 119.63 mm |
| September | 15.8 °C | 25.3 °C | 92.71 mm |
| October | 9.3 °C | 19.3 °C | 107.44 mm |
| November | 3.7 °C | 13.6 °C | 87.38 mm |
| December | -0.6 °C | 8.4 °C | 114.05 mm |
| Annual | 7.8 °C | 17.6 °C | 1202.95 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 50-75 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 | Extreme Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |