Ironton, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 35.2 °F (low) to 55.8 °F (high). Annual precipitation averages 38.1 Inches. Ironton is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.3 °F | 25.9 °F | 1.52 in. |
| February | 11.1 °F | 30.3 °F | 1.35 in. |
| March | 22.2 °F | 42.5 °F | 2.07 in. |
| April | 33.8 °F | 56.1 °F | 4.02 in. |
| May | 45.8 °F | 68.2 °F | 4.55 in. |
| June | 56.0 °F | 77.7 °F | 5.49 in. |
| July | 59.9 °F | 81.7 °F | 4.42 in. |
| August | 57.6 °F | 79.6 °F | 4.48 in. |
| September | 49.2 °F | 72.3 °F | 3.57 in. |
| October | 37.3 °F | 59.2 °F | 2.83 in. |
| November | 26.2 °F | 44.2 °F | 2.06 in. |
| December | 15.4 °F | 31.4 °F | 1.7 in. |
| Annual | 35.2 °F | 55.8 °F | 38.06 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |