Westfield, New Jersey has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.8 °C (low) to 17.7 °C (high). Annual precipitation averages 1240.6 Millimeters. Westfield is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.9 °C | 4.3 °C | 91.69 mm |
| February | -4.2 °C | 5.8 °C | 73.15 mm |
| March | -0.3 °C | 10.4 °C | 107.7 mm |
| April | 5.4 °C | 17.2 °C | 99.82 mm |
| May | 10.7 °C | 22.7 °C | 102.62 mm |
| June | 15.9 °C | 27.7 °C | 116.08 mm |
| July | 18.9 °C | 30.4 °C | 122.94 mm |
| August | 17.9 °C | 29.4 °C | 113.54 mm |
| September | 14.1 °C | 25.7 °C | 109.73 mm |
| October | 7.4 °C | 18.9 °C | 109.73 mm |
| November | 2.2 °C | 12.7 °C | 87.12 mm |
| December | -1.9 °C | 7.1 °C | 106.43 mm |
| Annual | 6.8 °C | 17.7 °C | 1240.55 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |