Frost Dates for 54660 — Tomah, Wisconsin

Half of springs at Mather 3 NW, WI see their last 32°F night by May 6; only one in ten is past it by April 24, and one in ten still has one after May 20. Planting tender crops after May 12 leaves a 30% risk of a frost on them, after May 15 20%, and after May 20 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 58% of the 182 Wisconsin stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 3 in half of years, as early as September 19 one year in ten, and holds off past October 16 one year in ten. A hard freeze of 28°F follows 12 days later, around October 15; in spring the one-in-ten date for 28°F is May 9, 11 days before the 32°F one. The freeze-free season lasts 148 days in a typical year, shorter than at 69% of the 182 Wisconsin stations; it reaches 167 days one year in ten and falls short of 129 one year in ten. On average 171 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 11 days longer, to about May 17, and return around September 23. Severe cold of 16°F or below comes every winter, usually between November 14 and March 29.

July is the warmest month at Mather 3 NW, WI, averaging 81°F by day and 58°F at night; January is the coldest at 24°F and 5°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 71% of years.

Warmth for growing adds up to 2,274 growing degree days a year (base 50°F), fewer than at 68% of the 182 Wisconsin stations. 33% of them (748) have built up by the end of June, and July adds the most, 606. Precipitation totals 35.2 inches a year, most in June (5.2") and least in February (1.0"); May to September bring 61% of it.

The nearest other station, Necedah 5 WNW, WI, 16 miles east of Tomah, has a last frost 5 days earlier (May 1), the same first-frost date, a season 9 days longer.

The first measurable snow (0.1 inch or more) in Tomah usually arrives around November 16, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Mather 3 NW, WI, 14.8 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 24 days after the last snow.

ZIP 54660 is 15 miles from Mather 3 NW, WI, which stands at 978 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 54660 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°C) over 1991–2020; a zone describes winter lows, not frost dates.