Garnavillo, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 36.7 °F (low) to 56.2 °F (high). Annual precipitation averages 38.1 Inches. Garnavillo 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.7 °F | 25.6 °F | 1.24 in. |
| February | 12.2 °F | 30.3 °F | 1.23 in. |
| March | 24.3 °F | 43.0 °F | 2.02 in. |
| April | 35.8 °F | 57.2 °F | 3.87 in. |
| May | 47.5 °F | 69.0 °F | 4.73 in. |
| June | 58.0 °F | 78.5 °F | 5.87 in. |
| July | 61.8 °F | 81.8 °F | 4.72 in. |
| August | 59.5 °F | 79.9 °F | 4.0 in. |
| September | 51.1 °F | 73.3 °F | 3.81 in. |
| October | 38.9 °F | 60.4 °F | 2.86 in. |
| November | 26.8 °F | 44.2 °F | 2.11 in. |
| December | 15.9 °F | 31.3 °F | 1.6 in. |
| Annual | 36.7 °F | 56.2 °F | 38.06 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°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 |