Mountain Iron, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -2.1 °C (low) to 9.6 °C (high). Annual precipitation averages 717.1 Millimeters. Mountain Iron is located in USDA Plant Hardiness Zone 3b. 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 | -19.4 °C | -8.2 °C | 24.13 mm |
| February | -17.8 °C | -4.9 °C | 19.05 mm |
| March | -10.4 °C | 2.3 °C | 27.69 mm |
| April | -2.7 °C | 9.9 °C | 48.77 mm |
| May | 4.3 °C | 17.6 °C | 76.2 mm |
| June | 10.1 °C | 22.7 °C | 107.7 mm |
| July | 12.7 °C | 25.3 °C | 105.92 mm |
| August | 11.3 °C | 24.3 °C | 83.57 mm |
| September | 7.2 °C | 19.4 °C | 88.14 mm |
| October | 0.7 °C | 11.1 °C | 68.83 mm |
| November | -7 °C | 1.5 °C | 38.1 mm |
| December | -14.5 °C | -5.4 °C | 28.96 mm |
| Annual | -2.1 °C | 9.6 °C | 717.06 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 3b : -37.2°C to -34.4°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |