Underwood, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.3 °C (low) to 16.3 °C (high). Annual precipitation averages 858 Millimeters. Underwood 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 | -10.7 °C | -0.1 °C | 18.03 mm |
| February | -8.4 °C | 2.6 °C | 24.89 mm |
| March | -2.4 °C | 9.8 °C | 45.21 mm |
| April | 3.7 °C | 17.1 °C | 85.85 mm |
| May | 10.5 °C | 22.8 °C | 135.64 mm |
| June | 16.4 °C | 28.3 °C | 129.79 mm |
| July | 18.7 °C | 30.3 °C | 95.25 mm |
| August | 17.2 °C | 29.2 °C | 103.63 mm |
| September | 11.9 °C | 25.7 °C | 78.23 mm |
| October | 4.9 °C | 18.4 °C | 67.56 mm |
| November | -2.1 °C | 9.5 °C | 39.37 mm |
| December | -7.7 °C | 2.3 °C | 34.54 mm |
| Annual | 4.3 °C | 16.3 °C | 857.99 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 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 |