Guernsey, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.8 °C (low) to 15 °C (high). Annual precipitation averages 947.2 Millimeters. Guernsey is located in USDA Plant Hardiness Zone 5b. 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 | -11.3 °C | -2 °C | 28.45 mm |
| February | -9.3 °C | 0.7 °C | 35.05 mm |
| March | -3.2 °C | 7.9 °C | 54.36 mm |
| April | 3.1 °C | 15.5 °C | 93.47 mm |
| May | 10.1 °C | 21.8 °C | 122.68 mm |
| June | 16.1 °C | 27.3 °C | 136.91 mm |
| July | 17.7 °C | 29.2 °C | 109.22 mm |
| August | 16.3 °C | 28.2 °C | 110.74 mm |
| September | 11.3 °C | 24.3 °C | 90.68 mm |
| October | 4.6 °C | 17.1 °C | 72.9 mm |
| November | -2.1 °C | 8.3 °C | 53.59 mm |
| December | -7.8 °C | 1.2 °C | 39.12 mm |
| Annual | 3.8 °C | 15 °C | 947.17 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 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 |