Grand Mound, 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 15.1 °C (high). Annual precipitation averages 976.9 Millimeters. Grand Mound 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 | -10.6 °C | -1.5 °C | 33.53 mm |
| February | -8.6 °C | 0.9 °C | 40.39 mm |
| March | -2.5 °C | 8.2 °C | 61.47 mm |
| April | 3.7 °C | 15.8 °C | 97.28 mm |
| May | 10.3 °C | 22 °C | 120.65 mm |
| June | 15.9 °C | 27.1 °C | 124.21 mm |
| July | 17.8 °C | 28.8 °C | 109.73 mm |
| August | 16.6 °C | 27.7 °C | 114.05 mm |
| September | 11.9 °C | 24.6 °C | 98.04 mm |
| October | 5.3 °C | 17.3 °C | 76.2 mm |
| November | -1.3 °C | 8.9 °C | 55.37 mm |
| December | -7.1 °C | 1.6 °C | 45.97 mm |
| Annual | 4.3 °C | 15.1 °C | 976.89 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 |