Portage, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.4 °C (low) to 13.7 °C (high). Annual precipitation averages 950.2 Millimeters. Portage is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.6 °C | -2.8 °C | 35.81 mm |
| February | -11.1 °C | -0.3 °C | 35.05 mm |
| March | -5.1 °C | 6.3 °C | 52.83 mm |
| April | 1.4 °C | 13.7 °C | 101.85 mm |
| May | 8.2 °C | 20.6 °C | 113.28 mm |
| June | 13.9 °C | 25.9 °C | 140.21 mm |
| July | 16.1 °C | 27.9 °C | 107.19 mm |
| August | 14.7 °C | 26.9 °C | 103.89 mm |
| September | 10.2 °C | 22.8 °C | 89.92 mm |
| October | 3.7 °C | 15.4 °C | 73.15 mm |
| November | -2.6 °C | 7.2 °C | 53.85 mm |
| December | -8.6 °C | 0.2 °C | 43.18 mm |
| Annual | 2.4 °C | 13.7 °C | 950.21 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |