Clayton, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.9 °C (low) to 13.7 °C (high). Annual precipitation averages 952.5 Millimeters. Clayton 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 | -12.6 °C | -3.2 °C | 31.75 mm |
| February | -10.7 °C | -0.6 °C | 31.24 mm |
| March | -4 °C | 6.4 °C | 50.55 mm |
| April | 2.4 °C | 14.2 °C | 96.27 mm |
| May | 8.9 °C | 20.7 °C | 117.6 mm |
| June | 14.7 °C | 26 °C | 147.07 mm |
| July | 16.8 °C | 27.9 °C | 117.6 mm |
| August | 15.6 °C | 26.9 °C | 98.81 mm |
| September | 10.9 °C | 23.2 °C | 97.03 mm |
| October | 4.2 °C | 15.9 °C | 71.37 mm |
| November | -2.5 °C | 7.2 °C | 52.83 mm |
| December | -8.6 °C | -0.1 °C | 40.39 mm |
| Annual | 2.9 °C | 13.7 °C | 952.51 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 |