West Branch, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.6 °F (low) to 59.7 °F (high). Annual precipitation averages 37.8 Inches. 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 | 13.0 °F | 29.6 °F | 1.28 in. |
| February | 16.6 °F | 34.1 °F | 1.53 in. |
| March | 27.5 °F | 47.2 °F | 2.32 in. |
| April | 38.7 °F | 61.3 °F | 3.75 in. |
| May | 50.5 °F | 72.0 °F | 4.74 in. |
| June | 60.6 °F | 81.2 °F | 5.2 in. |
| July | 64.1 °F | 84.5 °F | 4.31 in. |
| August | 61.6 °F | 82.7 °F | 4.22 in. |
| September | 53.0 °F | 76.7 °F | 3.53 in. |
| October | 41.1 °F | 63.6 °F | 2.96 in. |
| November | 29.2 °F | 48.2 °F | 2.22 in. |
| December | 18.9 °F | 34.9 °F | 1.72 in. |
| Annual | 39.6 °F | 59.7 °F | 37.78 in. |
| 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 : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |