Arnold, Missouri has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 47.2 °F (low) to 66.7 °F (high). Annual precipitation averages 44.3 Inches. Arnold 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 | 23.6 °F | 40.5 °F | 2.76 in. |
| February | 27.0 °F | 45.9 °F | 2.46 in. |
| March | 35.8 °F | 55.9 °F | 3.66 in. |
| April | 46.4 °F | 68.1 °F | 4.81 in. |
| May | 57.0 °F | 76.8 °F | 5.22 in. |
| June | 65.9 °F | 85.4 °F | 4.56 in. |
| July | 69.7 °F | 88.9 °F | 4.09 in. |
| August | 67.7 °F | 87.5 °F | 3.61 in. |
| September | 59.6 °F | 81.1 °F | 3.37 in. |
| October | 48.2 °F | 69.5 °F | 3.33 in. |
| November | 37.0 °F | 55.6 °F | 3.62 in. |
| December | 28.5 °F | 44.7 °F | 2.82 in. |
| Annual | 47.2 °F | 66.7 °F | 44.31 in. |
| 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 : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |