Marengo, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.1 °C (low) to 10.9 °C (high). Annual precipitation averages 824.5 Millimeters. Marengo is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -15.1 °C | -5.5 °C | 34.8 mm |
| February | -13.8 °C | -3 °C | 28.19 mm |
| March | -8.2 °C | 2.9 °C | 41.91 mm |
| April | -1.5 °C | 9.7 °C | 73.41 mm |
| May | 4.4 °C | 17.5 °C | 93.73 mm |
| June | 10.2 °C | 22.7 °C | 100.33 mm |
| July | 13.6 °C | 25.7 °C | 110.49 mm |
| August | 12.8 °C | 24.9 °C | 88.14 mm |
| September | 8.7 °C | 20.7 °C | 84.33 mm |
| October | 2.2 °C | 12.7 °C | 81.53 mm |
| November | -3.8 °C | 4.7 °C | 46.48 mm |
| December | -10.6 °C | -2.6 °C | 41.15 mm |
| Annual | -0.1 °C | 10.9 °C | 824.49 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |