Eureka, Missouri has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 45.5 °F (low) to 66.2 °F (high). Annual precipitation averages 43.9 Inches. Eureka is located in USDA Plant Hardiness Zone 6b. 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 | 21.7 °F | 39.6 °F | 2.77 in. |
| February | 25.4 °F | 45.3 °F | 2.4 in. |
| March | 34.1 °F | 55.4 °F | 3.68 in. |
| April | 44.7 °F | 67.7 °F | 4.76 in. |
| May | 55.6 °F | 76.4 °F | 5.19 in. |
| June | 64.5 °F | 84.8 °F | 4.49 in. |
| July | 68.6 °F | 88.6 °F | 3.98 in. |
| August | 66.3 °F | 87.3 °F | 3.63 in. |
| September | 57.8 °F | 80.8 °F | 3.41 in. |
| October | 45.6 °F | 69.1 °F | 3.33 in. |
| November | 34.9 °F | 55.5 °F | 3.55 in. |
| December | 26.2 °F | 44.3 °F | 2.7 in. |
| Annual | 45.5 °F | 66.2 °F | 43.89 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 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |