Ironton, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.4 °C (low) to 12.1 °C (high). Annual precipitation averages 858.3 Millimeters. Ironton is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.3 °C | -2.4 °C | 57.15 mm |
| February | -10.2 °C | -1.5 °C | 37.85 mm |
| March | -6.6 °C | 3.6 °C | 45.21 mm |
| April | -0.2 °C | 10.7 °C | 70.36 mm |
| May | 5.9 °C | 18.1 °C | 76.96 mm |
| June | 11.6 °C | 23 °C | 76.2 mm |
| July | 14.5 °C | 25.4 °C | 69.85 mm |
| August | 14.2 °C | 25.1 °C | 81.03 mm |
| September | 10.3 °C | 21.3 °C | 92.96 mm |
| October | 4.5 °C | 13.8 °C | 108.97 mm |
| November | -0.5 °C | 6.7 °C | 73.91 mm |
| December | -5.2 °C | 0.8 °C | 67.82 mm |
| Annual | 2.4 °C | 12.1 °C | 858.27 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |