Coulter, 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 13.4 °C (high). Annual precipitation averages 928.4 Millimeters. Coulter 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 | -13.6 °C | -3.9 °C | 22.86 mm |
| February | -11.3 °C | -1.3 °C | 26.92 mm |
| March | -4.6 °C | 5.7 °C | 52.07 mm |
| April | 1.7 °C | 14.1 °C | 98.55 mm |
| May | 8.8 °C | 20.7 °C | 129.79 mm |
| June | 14.7 °C | 26.2 °C | 148.59 mm |
| July | 16.3 °C | 27.8 °C | 114.3 mm |
| August | 14.7 °C | 26.7 °C | 107.7 mm |
| September | 9.8 °C | 23.4 °C | 83.57 mm |
| October | 3.1 °C | 15.9 °C | 64.26 mm |
| November | -3.6 °C | 6.8 °C | 44.45 mm |
| December | -9.7 °C | -0.8 °C | 35.31 mm |
| Annual | 2.2 °C | 13.4 °C | 928.37 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |