Smithville, Tennessee has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.7 °C (low) to 20.5 °C (high). Annual precipitation averages 1444.8 Millimeters. Smithville is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.9 °C | 8.3 °C | 125.73 mm |
| February | -1.6 °C | 10.8 °C | 121.16 mm |
| March | 2.1 °C | 15.4 °C | 142.49 mm |
| April | 6.5 °C | 21 °C | 127.51 mm |
| May | 12.1 °C | 25.3 °C | 127.51 mm |
| June | 16.8 °C | 29.1 °C | 134.87 mm |
| July | 19.1 °C | 30.7 °C | 129.03 mm |
| August | 18.1 °C | 30.4 °C | 98.81 mm |
| September | 14.2 °C | 27.4 °C | 99.06 mm |
| October | 7.3 °C | 21.9 °C | 84.58 mm |
| November | 1.5 °C | 15.5 °C | 102.62 mm |
| December | -1.2 °C | 10.4 °C | 151.38 mm |
| Annual | 7.7 °C | 20.5 °C | 1444.75 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |