Iron Mountain, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 30.6 °F (low) to 52.6 °F (high). Annual precipitation averages 29.4 Inches. 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 | 4.4 °F | 23.3 °F | 1.32 in. |
| February | 5.2 °F | 27.4 °F | 1.16 in. |
| March | 15.1 °F | 38.4 °F | 1.59 in. |
| April | 28.0 °F | 51.3 °F | 2.67 in. |
| May | 40.5 °F | 65.7 °F | 2.96 in. |
| June | 50.6 °F | 74.9 °F | 3.41 in. |
| July | 54.9 °F | 79.4 °F | 3.25 in. |
| August | 53.0 °F | 77.2 °F | 2.92 in. |
| September | 45.6 °F | 69.3 °F | 3.24 in. |
| October | 34.1 °F | 55.0 °F | 3.3 in. |
| November | 23.8 °F | 40.3 °F | 1.88 in. |
| December | 12.0 °F | 28.4 °F | 1.68 in. |
| Annual | 30.6 °F | 52.6 °F | 29.38 in. |
| 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 : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |