Mountain Iron, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 28.2 °F (low) to 49.3 °F (high). Annual precipitation averages 28.2 Inches. 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 | -3.0 °F | 17.2 °F | 0.95 in. |
| February | -0.1 °F | 23.2 °F | 0.75 in. |
| March | 13.2 °F | 36.1 °F | 1.09 in. |
| April | 27.1 °F | 49.8 °F | 1.92 in. |
| May | 39.7 °F | 63.7 °F | 3.0 in. |
| June | 50.2 °F | 72.9 °F | 4.24 in. |
| July | 54.9 °F | 77.5 °F | 4.17 in. |
| August | 52.3 °F | 75.7 °F | 3.29 in. |
| September | 45.0 °F | 66.9 °F | 3.47 in. |
| October | 33.3 °F | 51.9 °F | 2.71 in. |
| November | 19.4 °F | 34.7 °F | 1.5 in. |
| December | 5.9 °F | 22.2 °F | 1.14 in. |
| Annual | 28.2 °F | 49.3 °F | 28.23 in. |
| 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 : -35°F to -30°F |
| Plant Hardiness Zone - 2012 | Zone 3b : -35°F to -30°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |