Glenwood, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.5 °C (low) to 16.5 °C (high). Annual precipitation averages 851.9 Millimeters. Glenwood is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.3 °C | 0.3 °C | 19.05 mm |
| February | -8.2 °C | 3.1 °C | 24.89 mm |
| March | -2.1 °C | 10.4 °C | 45.97 mm |
| April | 3.8 °C | 17.2 °C | 89.92 mm |
| May | 10.6 °C | 22.8 °C | 137.67 mm |
| June | 16.4 °C | 28.3 °C | 133.86 mm |
| July | 18.8 °C | 30.1 °C | 97.03 mm |
| August | 17.3 °C | 29.3 °C | 94.23 mm |
| September | 11.9 °C | 25.7 °C | 78.49 mm |
| October | 5 °C | 18.6 °C | 64.01 mm |
| November | -2.1 °C | 9.8 °C | 38.1 mm |
| December | -7.6 °C | 2.8 °C | 28.7 mm |
| Annual | 4.5 °C | 16.5 °C | 851.92 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |