Westby, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 36.5 °F (low) to 54.1 °F (high). Annual precipitation averages 36.8 Inches. Westby 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 Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.7 °F | 23.6 °F | 1.1 in. |
| February | 12.4 °F | 28.4 °F | 1.0 in. |
| March | 23.4 °F | 40.8 °F | 1.77 in. |
| April | 35.4 °F | 55.3 °F | 3.82 in. |
| May | 47.3 °F | 67.3 °F | 4.71 in. |
| June | 57.4 °F | 76.2 °F | 5.42 in. |
| July | 61.4 °F | 80.2 °F | 4.51 in. |
| August | 59.3 °F | 78.2 °F | 4.59 in. |
| September | 51.0 °F | 70.9 °F | 3.84 in. |
| October | 39.3 °F | 57.7 °F | 2.71 in. |
| November | 26.8 °F | 41.9 °F | 1.86 in. |
| December | 15.7 °F | 29.2 °F | 1.47 in. |
| Annual | 36.5 °F | 54.1 °F | 36.8 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| 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 |