Iron Mountain, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.8 °C (low) to 11.4 °C (high). Annual precipitation averages 746.3 Millimeters. Iron Mountain 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 | -15.3 °C | -4.8 °C | 33.53 mm |
| February | -14.9 °C | -2.6 °C | 29.46 mm |
| March | -9.4 °C | 3.6 °C | 40.39 mm |
| April | -2.2 °C | 10.7 °C | 67.82 mm |
| May | 4.7 °C | 18.7 °C | 75.18 mm |
| June | 10.3 °C | 23.8 °C | 86.61 mm |
| July | 12.7 °C | 26.3 °C | 82.55 mm |
| August | 11.7 °C | 25.1 °C | 74.17 mm |
| September | 7.6 °C | 20.7 °C | 82.3 mm |
| October | 1.2 °C | 12.8 °C | 83.82 mm |
| November | -4.6 °C | 4.6 °C | 47.75 mm |
| December | -11.1 °C | -2 °C | 42.67 mm |
| Annual | -0.8 °C | 11.4 °C | 746.25 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |