Iron River, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.2 °C (low) to 10.8 °C (high). Annual precipitation averages 835.9 Millimeters. Iron River is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -17.1 °C | -6.3 °C | 29.97 mm |
| February | -15.5 °C | -3.2 °C | 26.67 mm |
| March | -9.1 °C | 3.3 °C | 43.43 mm |
| April | -2.2 °C | 10.5 °C | 70.87 mm |
| May | 4.2 °C | 18.3 °C | 88.9 mm |
| June | 9.8 °C | 23.3 °C | 104.39 mm |
| July | 12.9 °C | 25.9 °C | 109.47 mm |
| August | 11.9 °C | 24.9 °C | 96.77 mm |
| September | 7.7 °C | 20.4 °C | 88.9 mm |
| October | 1.2 °C | 12.4 °C | 82.04 mm |
| November | -5.2 °C | 3.8 °C | 52.83 mm |
| December | -12.4 °C | -3.4 °C | 41.66 mm |
| Annual | -1.2 °C | 10.8 °C | 835.9 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4a : -34.4°C to -31.7°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 |