Tomah, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.3 °C (low) to 13 °C (high). Annual precipitation averages 925.6 Millimeters. Tomah is located in USDA Plant Hardiness Zone 4b. 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 | -13.9 °C | -3.8 °C | 30.48 mm |
| February | -12.3 °C | -1.1 °C | 28.7 mm |
| March | -6 °C | 5.6 °C | 47.5 mm |
| April | 0.7 °C | 13.3 °C | 94.74 mm |
| May | 7.4 °C | 20.1 °C | 115.06 mm |
| June | 12.9 °C | 25.3 °C | 135.64 mm |
| July | 15.1 °C | 27.5 °C | 108.97 mm |
| August | 13.7 °C | 26.3 °C | 112.01 mm |
| September | 9.1 °C | 22.2 °C | 95.25 mm |
| October | 2.8 °C | 14.8 °C | 70.87 mm |
| November | -3.6 °C | 6.3 °C | 47.75 mm |
| December | -9.8 °C | -0.8 °C | 38.61 mm |
| Annual | 1.3 °C | 13 °C | 925.58 mm |
| 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 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |