Hartwick, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.7 °C (low) to 14.7 °C (high). Annual precipitation averages 933.7 Millimeters. Hartwick 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.4 °C | -2.6 °C | 28.19 mm |
| February | -9.6 °C | 0.2 °C | 33.78 mm |
| March | -3.3 °C | 7.4 °C | 53.85 mm |
| April | 2.8 °C | 15.2 °C | 92.2 mm |
| May | 10 °C | 21.8 °C | 119.89 mm |
| June | 16.2 °C | 27.3 °C | 136.4 mm |
| July | 17.9 °C | 29.1 °C | 106.68 mm |
| August | 16.2 °C | 28.1 °C | 107.44 mm |
| September | 11.2 °C | 24.1 °C | 90.93 mm |
| October | 4.6 °C | 16.7 °C | 72.39 mm |
| November | -2.2 °C | 8 °C | 52.83 mm |
| December | -7.9 °C | 0.7 °C | 39.12 mm |
| Annual | 3.7 °C | 14.7 °C | 933.7 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 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 |