Iron Junction, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -2.5 °C (low) to 9.7 °C (high). Annual precipitation averages 710.7 Millimeters. Iron Junction 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 | -19.7 °C | -8 °C | 23.37 mm |
| February | -18.2 °C | -4.8 °C | 18.54 mm |
| March | -10.8 °C | 2.3 °C | 26.67 mm |
| April | -3.1 °C | 9.9 °C | 47.75 mm |
| May | 3.8 °C | 17.5 °C | 76.2 mm |
| June | 9.7 °C | 22.7 °C | 107.19 mm |
| July | 12.2 °C | 25.3 °C | 105.92 mm |
| August | 10.8 °C | 24.3 °C | 83.31 mm |
| September | 6.5 °C | 19.4 °C | 87.38 mm |
| October | 0.3 °C | 11.2 °C | 68.07 mm |
| November | -6.9 °C | 1.8 °C | 37.08 mm |
| December | -14.7 °C | -5.1 °C | 29.21 mm |
| Annual | -2.5 °C | 9.7 °C | 710.69 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 |