Altoona, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4 °C (low) to 15.4 °C (high). Annual precipitation averages 911.1 Millimeters. Altoona 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 | -11.1 °C | -1.2 °C | 24.13 mm |
| February | -8.9 °C | 1.3 °C | 29.72 mm |
| March | -2.8 °C | 8.5 °C | 52.58 mm |
| April | 3.5 °C | 16.2 °C | 95.76 mm |
| May | 10.2 °C | 21.9 °C | 127.51 mm |
| June | 16 °C | 27.3 °C | 134.62 mm |
| July | 18 °C | 29.4 °C | 108.46 mm |
| August | 16.6 °C | 28.4 °C | 106.17 mm |
| September | 11.7 °C | 24.8 °C | 86.11 mm |
| October | 4.8 °C | 17.4 °C | 66.04 mm |
| November | -1.9 °C | 8.9 °C | 45.97 mm |
| December | -7.8 °C | 1.7 °C | 34.04 mm |
| Annual | 4 °C | 15.4 °C | 911.11 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 |