West Branch, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.2 °C (low) to 15.4 °C (high). Annual precipitation averages 959.6 Millimeters. West Branch is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.6 °C | -1.3 °C | 32.51 mm |
| February | -8.6 °C | 1.2 °C | 38.86 mm |
| March | -2.5 °C | 8.4 °C | 58.93 mm |
| April | 3.7 °C | 16.3 °C | 95.25 mm |
| May | 10.3 °C | 22.2 °C | 120.4 mm |
| June | 15.9 °C | 27.3 °C | 132.08 mm |
| July | 17.8 °C | 29.2 °C | 109.47 mm |
| August | 16.4 °C | 28.2 °C | 107.19 mm |
| September | 11.7 °C | 24.8 °C | 89.66 mm |
| October | 5.1 °C | 17.6 °C | 75.18 mm |
| November | -1.6 °C | 9 °C | 56.39 mm |
| December | -7.3 °C | 1.6 °C | 43.69 mm |
| Annual | 4.2 °C | 15.4 °C | 959.61 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |