New Haven, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.2 °C (low) to 13.1 °C (high). Annual precipitation averages 947.2 Millimeters. New Haven 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 | -13.7 °C | -4.4 °C | 24.89 mm |
| February | -11.5 °C | -2 °C | 28.45 mm |
| March | -4.8 °C | 5.1 °C | 47.75 mm |
| April | 1.8 °C | 13.7 °C | 99.06 mm |
| May | 8.6 °C | 20.6 °C | 128.27 mm |
| June | 14.5 °C | 25.9 °C | 150.37 mm |
| July | 16.3 °C | 27.7 °C | 117.35 mm |
| August | 14.9 °C | 26.4 °C | 105.92 mm |
| September | 10.2 °C | 23.1 °C | 93.98 mm |
| October | 3.3 °C | 15.6 °C | 70.1 mm |
| November | -3.5 °C | 6.3 °C | 44.45 mm |
| December | -9.8 °C | -1.3 °C | 36.58 mm |
| Annual | 2.2 °C | 13.1 °C | 947.17 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |