Thayer, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.3 °F (low) to 60.3 °F (high). Annual precipitation averages 36.9 Inches. 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 | 12.7 °F | 31.3 °F | 0.95 in. |
| February | 16.7 °F | 36.1 °F | 1.33 in. |
| March | 27.4 °F | 48.9 °F | 2.13 in. |
| April | 38.2 °F | 61.4 °F | 3.78 in. |
| May | 50.0 °F | 71.3 °F | 5.43 in. |
| June | 60.2 °F | 80.8 °F | 4.93 in. |
| July | 64.4 °F | 85.2 °F | 4.25 in. |
| August | 61.9 °F | 83.6 °F | 4.08 in. |
| September | 52.8 °F | 76.3 °F | 3.79 in. |
| October | 40.6 °F | 64.0 °F | 2.64 in. |
| November | 28.7 °F | 49.0 °F | 2.14 in. |
| December | 18.3 °F | 36.2 °F | 1.48 in. |
| Annual | 39.3 °F | 60.3 °F | 36.93 in. |
| 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 : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |