Thayer, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.1 °C (low) to 15.7 °C (high). Annual precipitation averages 938 Millimeters. Thayer 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 | -10.7 °C | -0.4 °C | 24.13 mm |
| February | -8.5 °C | 2.3 °C | 33.78 mm |
| March | -2.6 °C | 9.4 °C | 54.1 mm |
| April | 3.4 °C | 16.3 °C | 96.01 mm |
| May | 10 °C | 21.8 °C | 137.92 mm |
| June | 15.7 °C | 27.1 °C | 125.22 mm |
| July | 18 °C | 29.6 °C | 107.95 mm |
| August | 16.6 °C | 28.7 °C | 103.63 mm |
| September | 11.6 °C | 24.6 °C | 96.27 mm |
| October | 4.8 °C | 17.8 °C | 67.06 mm |
| November | -1.8 °C | 9.4 °C | 54.36 mm |
| December | -7.6 °C | 2.3 °C | 37.59 mm |
| Annual | 4.1 °C | 15.7 °C | 938.02 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 |