Walnut Grove, Missouri has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.5 °C (low) to 19.5 °C (high). Annual precipitation averages 1150.1 Millimeters. Walnut Grove is located in USDA Plant Hardiness Zone 6b. 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 | -5.1 °C | 5.9 °C | 58.93 mm |
| February | -3.2 °C | 8.7 °C | 55.88 mm |
| March | 1.6 °C | 14.1 °C | 90.68 mm |
| April | 6.8 °C | 19.6 °C | 120.4 mm |
| May | 12.6 °C | 24.1 °C | 147.32 mm |
| June | 17.5 °C | 28.9 °C | 117.86 mm |
| July | 19.8 °C | 31.4 °C | 103.89 mm |
| August | 18.8 °C | 31.3 °C | 91.44 mm |
| September | 14.3 °C | 27.2 °C | 116.59 mm |
| October | 7.7 °C | 20.8 °C | 91.19 mm |
| November | 1.8 °C | 13.7 °C | 89.15 mm |
| December | -3 °C | 7.9 °C | 66.8 mm |
| Annual | 7.5 °C | 19.5 °C | 1150.13 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 6b : -20.6°C to -17.8°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 |