Mount Vernon, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.8 °C (low) to 24.1 °C (high). Annual precipitation averages 1213.1 Millimeters. Mount Vernon is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.1 °C | 12.9 °C | 83.31 mm |
| February | 3 °C | 15.2 °C | 95.5 mm |
| March | 6.9 °C | 19.6 °C | 113.79 mm |
| April | 10.8 °C | 23.8 °C | 107.19 mm |
| May | 16.3 °C | 27.8 °C | 126.75 mm |
| June | 20.7 °C | 31.9 °C | 105.66 mm |
| July | 22.6 °C | 34.3 °C | 79.25 mm |
| August | 21.9 °C | 34.6 °C | 71.63 mm |
| September | 18.2 °C | 31.1 °C | 93.98 mm |
| October | 11.9 °C | 25.2 °C | 120.4 mm |
| November | 6.4 °C | 18.9 °C | 98.04 mm |
| December | 2.3 °C | 14.1 °C | 117.6 mm |
| Annual | 11.8 °C | 24.1 °C | 1213.1 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |