Westfield, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.7 °C (low) to 15.3 °C (high). Annual precipitation averages 734.6 Millimeters. Westfield is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.7 °C | -1.8 °C | 15.75 mm |
| February | -10.4 °C | 1.1 °C | 19.05 mm |
| March | -4.1 °C | 8.2 °C | 41.66 mm |
| April | 2.1 °C | 16 °C | 78.74 mm |
| May | 9 °C | 22.2 °C | 103.38 mm |
| June | 15.3 °C | 27.9 °C | 114.55 mm |
| July | 17.2 °C | 29.7 °C | 83.82 mm |
| August | 15.8 °C | 28.6 °C | 83.57 mm |
| September | 10.6 °C | 24.9 °C | 74.68 mm |
| October | 3.3 °C | 17.6 °C | 62.74 mm |
| November | -3.9 °C | 8.3 °C | 33.27 mm |
| December | -9.8 °C | 0.6 °C | 23.37 mm |
| Annual | 2.7 °C | 15.3 °C | 734.58 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |