Marengo, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 31.8 °F (low) to 51.5 °F (high). Annual precipitation averages 32.5 Inches. 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 | 4.9 °F | 22.1 °F | 1.37 in. |
| February | 7.1 °F | 26.6 °F | 1.11 in. |
| March | 17.3 °F | 37.2 °F | 1.65 in. |
| April | 29.3 °F | 49.4 °F | 2.89 in. |
| May | 39.9 °F | 63.5 °F | 3.69 in. |
| June | 50.4 °F | 72.9 °F | 3.95 in. |
| July | 56.4 °F | 78.2 °F | 4.35 in. |
| August | 55.0 °F | 76.9 °F | 3.47 in. |
| September | 47.7 °F | 69.2 °F | 3.32 in. |
| October | 35.9 °F | 54.8 °F | 3.21 in. |
| November | 25.2 °F | 40.4 °F | 1.83 in. |
| December | 12.9 °F | 27.3 °F | 1.62 in. |
| Annual | 31.8 °F | 51.5 °F | 32.46 in. |
| 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 : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |