Alta, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 37.6 °F (low) to 56.9 °F (high). Annual precipitation averages 32.2 Inches. Alta 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 | 9.1 °F | 25.9 °F | 0.74 in. |
| February | 13.2 °F | 30.1 °F | 0.91 in. |
| March | 25.4 °F | 44.1 °F | 1.75 in. |
| April | 36.3 °F | 58.1 °F | 3.54 in. |
| May | 49.2 °F | 70.1 °F | 4.44 in. |
| June | 60.2 °F | 80.1 °F | 5.19 in. |
| July | 63.3 °F | 82.2 °F | 3.42 in. |
| August | 60.5 °F | 79.8 °F | 4.4 in. |
| September | 52.1 °F | 74.8 °F | 2.99 in. |
| October | 39.6 °F | 61.6 °F | 2.31 in. |
| November | 26.5 °F | 44.9 °F | 1.46 in. |
| December | 15.4 °F | 31.0 °F | 1.05 in. |
| Annual | 37.6 °F | 56.9 °F | 32.2 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |