Grundy Center, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3 °C (low) to 14.2 °C (high). Annual precipitation averages 930.4 Millimeters. Grundy Center is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.6 °C | -3.1 °C | 23.11 mm |
| February | -10.3 °C | -0.4 °C | 27.43 mm |
| March | -3.9 °C | 6.9 °C | 53.09 mm |
| April | 2.3 °C | 14.9 °C | 97.28 mm |
| May | 9.4 °C | 21.3 °C | 123.7 mm |
| June | 15.3 °C | 26.7 °C | 147.07 mm |
| July | 17.1 °C | 28.3 °C | 108.71 mm |
| August | 15.5 °C | 27.3 °C | 111 mm |
| September | 10.6 °C | 24 °C | 84.58 mm |
| October | 3.9 °C | 16.7 °C | 69.09 mm |
| November | -2.9 °C | 7.6 °C | 48.26 mm |
| December | -8.9 °C | 0.2 °C | 37.08 mm |
| Annual | 3 °C | 14.2 °C | 930.4 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°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 |