Mehlville, Missouri has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.6 °C (low) to 19.3 °C (high). Annual precipitation averages 1141 Millimeters. Mehlville is located in USDA Plant Hardiness Zone 7a. 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 | -4.4 °C | 4.8 °C | 70.36 mm |
| February | -2.6 °C | 7.8 °C | 63.5 mm |
| March | 2.2 °C | 13.4 °C | 92.2 mm |
| April | 8.2 °C | 20.2 °C | 120.14 mm |
| May | 14.1 °C | 25 °C | 134.62 mm |
| June | 18.9 °C | 29.7 °C | 118.11 mm |
| July | 21.2 °C | 31.7 °C | 105.92 mm |
| August | 20 °C | 30.9 °C | 95.76 mm |
| September | 15.6 °C | 27.3 °C | 85.85 mm |
| October | 9.4 °C | 20.8 °C | 89.15 mm |
| November | 2.9 °C | 13 °C | 93.98 mm |
| December | -1.8 °C | 7.1 °C | 71.37 mm |
| Annual | 8.6 °C | 19.3 °C | 1140.96 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 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |