Ironton, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7 °C (low) to 19.6 °C (high). Annual precipitation averages 1189.7 Millimeters. Ironton 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 | -5.1 °C | 6 °C | 66.55 mm |
| February | -3.3 °C | 9.1 °C | 69.09 mm |
| March | 1.1 °C | 14.4 °C | 99.31 mm |
| April | 6.6 °C | 20.7 °C | 145.8 mm |
| May | 12.1 °C | 24.7 °C | 142.24 mm |
| June | 16.6 °C | 28.9 °C | 103.38 mm |
| July | 18.9 °C | 31 °C | 95 mm |
| August | 17.8 °C | 30.7 °C | 96.77 mm |
| September | 13.4 °C | 27.1 °C | 90.93 mm |
| October | 7.1 °C | 21.2 °C | 84.58 mm |
| November | 1.3 °C | 13.6 °C | 117.09 mm |
| December | -2.9 °C | 7.7 °C | 78.99 mm |
| Annual | 7 °C | 19.6 °C | 1189.73 mm |
| 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 : -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 | Dfa - Humid Continental Hot Summers With Year Around Precipitation |