Alto, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 12.9 °C (low) to 25.3 °C (high). Annual precipitation averages 1226 Millimeters. Alto is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 1 - Mar. 10 through the first frost around Nov. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.8 °C | 14.9 °C | 111.76 mm |
| February | 4.8 °C | 17.2 °C | 97.79 mm |
| March | 8.4 °C | 21.1 °C | 109.98 mm |
| April | 12.2 °C | 25.1 °C | 94.23 mm |
| May | 17.3 °C | 29.1 °C | 110.74 mm |
| June | 21.2 °C | 32.5 °C | 112.27 mm |
| July | 22.4 °C | 34.4 °C | 67.82 mm |
| August | 22.2 °C | 34.9 °C | 88.39 mm |
| September | 18.9 °C | 31.6 °C | 90.42 mm |
| October | 13.1 °C | 26.3 °C | 115.82 mm |
| November | 7.6 °C | 20.3 °C | 110.49 mm |
| December | 3.8 °C | 15.8 °C | 116.33 mm |
| Annual | 12.9 °C | 25.3 °C | 1226.04 mm |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| Average Last Frost Date | Mar. 1 - Mar. 10 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |