Harviell, Missouri has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.2 °C (low) to 20.4 °C (high). Annual precipitation averages 1276.9 Millimeters. Harviell is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.1 °C | 6.7 °C | 88.39 mm |
| February | -1.2 °C | 9.5 °C | 90.68 mm |
| March | 3.3 °C | 14.8 °C | 115.82 mm |
| April | 8.8 °C | 21.1 °C | 144.78 mm |
| May | 14.4 °C | 25.8 °C | 132.33 mm |
| June | 19.5 °C | 30.4 °C | 95.5 mm |
| July | 21.4 °C | 31.9 °C | 109.73 mm |
| August | 20.1 °C | 31.4 °C | 84.84 mm |
| September | 15.7 °C | 28.1 °C | 90.68 mm |
| October | 8.9 °C | 22.2 °C | 98.55 mm |
| November | 3.2 °C | 14.6 °C | 118.36 mm |
| December | -1.2 °C | 8.4 °C | 107.19 mm |
| Annual | 9.2 °C | 20.4 °C | 1276.85 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : -15°C to -12.2°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 |