Irondale, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 44.5 °F (low) to 66.6 °F (high). Annual precipitation averages 45.2 Inches. Irondale 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 22.4 °F | 41.8 °F | 2.67 in. |
| February | 25.5 °F | 47.1 °F | 2.65 in. |
| March | 33.6 °F | 56.8 °F | 3.88 in. |
| April | 43.8 °F | 68.0 °F | 5.29 in. |
| May | 53.8 °F | 75.9 °F | 5.38 in. |
| June | 62.1 °F | 83.8 °F | 4.12 in. |
| July | 66.4 °F | 87.5 °F | 3.9 in. |
| August | 64.4 °F | 87.0 °F | 3.55 in. |
| September | 56.4 °F | 80.2 °F | 3.37 in. |
| October | 44.7 °F | 69.4 °F | 3.38 in. |
| November | 34.4 °F | 56.0 °F | 3.95 in. |
| December | 26.6 °F | 45.1 °F | 3.02 in. |
| Annual | 44.5 °F | 66.6 °F | 45.16 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |