Smithville, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.4 °C (low) to 22.9 °C (high). Annual precipitation averages 1429 Millimeters. Smithville is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -1.8 °C | 11.5 °C | 99.57 mm |
| February | 0.1 °C | 13.8 °C | 96.52 mm |
| March | 4.2 °C | 18.2 °C | 125.48 mm |
| April | 8.4 °C | 22.7 °C | 138.94 mm |
| May | 14.1 °C | 26.3 °C | 176.78 mm |
| June | 18.6 °C | 30.7 °C | 110.24 mm |
| July | 20.4 °C | 33.1 °C | 100.84 mm |
| August | 19.7 °C | 33.8 °C | 89.92 mm |
| September | 16 °C | 30.1 °C | 112.78 mm |
| October | 9.4 °C | 23.9 °C | 137.92 mm |
| November | 4 °C | 17.6 °C | 116.33 mm |
| December | -0.2 °C | 12.5 °C | 123.7 mm |
| Annual | 9.4 °C | 22.9 °C | 1429.02 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |