Union, New Jersey has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.3 °C (low) to 17.7 °C (high). Annual precipitation averages 1226.8 Millimeters. Union is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.5 °C | 4.3 °C | 90.17 mm |
| February | -3.7 °C | 5.8 °C | 73.66 mm |
| March | 0.1 °C | 10.3 °C | 105.92 mm |
| April | 5.7 °C | 17.1 °C | 99.57 mm |
| May | 11.1 °C | 22.6 °C | 103.12 mm |
| June | 16.4 °C | 27.6 °C | 113.79 mm |
| July | 19.4 °C | 30.4 °C | 119.63 mm |
| August | 18.6 °C | 29.4 °C | 114.05 mm |
| September | 14.7 °C | 25.7 °C | 105.92 mm |
| October | 8.1 °C | 18.9 °C | 111.76 mm |
| November | 2.7 °C | 12.7 °C | 85.85 mm |
| December | -1.3 °C | 7.1 °C | 103.38 mm |
| Annual | 7.3 °C | 17.7 °C | 1226.82 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 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 | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |