Plain, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 35.9 °F (low) to 56.5 °F (high). Annual precipitation averages 37.6 Inches. Plain 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 Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 9.1 °F | 26.8 °F | 1.4 in. |
| February | 11.7 °F | 31.1 °F | 1.36 in. |
| March | 22.8 °F | 43.3 °F | 2.04 in. |
| April | 34.5 °F | 56.8 °F | 4.0 in. |
| May | 46.4 °F | 68.9 °F | 4.47 in. |
| June | 56.9 °F | 78.4 °F | 5.47 in. |
| July | 60.6 °F | 82.0 °F | 4.58 in. |
| August | 58.4 °F | 80.2 °F | 4.16 in. |
| September | 49.9 °F | 73.0 °F | 3.56 in. |
| October | 38.1 °F | 60.1 °F | 2.79 in. |
| November | 26.8 °F | 44.9 °F | 2.13 in. |
| December | 16.0 °F | 32.2 °F | 1.63 in. |
| Annual | 35.9 °F | 56.5 °F | 37.59 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 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 |