Ironwood, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.1 °C (low) to 10.1 °C (high). Annual precipitation averages 920 Millimeters. Ironwood is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -16.3 °C | -6.5 °C | 50.8 mm |
| February | -15.7 °C | -3.9 °C | 36.07 mm |
| March | -10.2 °C | 2.4 °C | 46.74 mm |
| April | -2.6 °C | 9.3 °C | 74.93 mm |
| May | 4.7 °C | 17.3 °C | 92.71 mm |
| June | 10.3 °C | 22.6 °C | 99.06 mm |
| July | 12.9 °C | 24.8 °C | 105.16 mm |
| August | 11.7 °C | 23.8 °C | 94.49 mm |
| September | 7.7 °C | 19.5 °C | 95.5 mm |
| October | 1.1 °C | 11.5 °C | 97.03 mm |
| November | -5.2 °C | 3.2 °C | 68.33 mm |
| December | -11.9 °C | -3.4 °C | 59.18 mm |
| Annual | -1.1 °C | 10.1 °C | 920 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |