Frost Dates for 54968 — Princeton, Wisconsin

Half of springs at Montello, WI see their last 32°F night by May 3; only one in ten is past it by April 21, and one in ten still has one after May 18. Planting tender crops after May 9 leaves a 30% risk of a frost on them, after May 13 20%, and after May 18 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 30% of the 182 Wisconsin stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 5 in half of years, as early as September 22 one year in ten, and holds off past October 18 one year in ten. A hard freeze of 28°F follows 11 days later, around October 16; in spring the one-in-ten date for 28°F is May 6, 12 days before the 32°F one. The freeze-free season lasts 153 days in a typical year, shorter than at 57% of the 182 Wisconsin stations; it reaches 172 days one year in ten and falls short of 132 one year in ten. On average 160 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 12 days longer, to about May 15, and return around September 27. Severe cold of 16°F or below comes every winter, usually between November 18 and March 23.

July is the warmest month at Montello, WI, averaging 82°F by day and 60°F at night; January is the coldest at 26°F and 8°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 60% of years.

Warmth for growing adds up to 2,497 growing degree days a year (base 50°F), more than at 58% of the 182 Wisconsin stations. 33% of them (832) have built up by the end of June, and July adds the most, 643. Precipitation totals 36.4 inches a year, most in June (5.0") and least in February (1.3"); May to September bring 59% of it.

The nearest other station, Markesan, WI, 12 miles southeast of Princeton, has a last frost 5 days later (May 8), a first frost 3 days earlier (October 2), a season 9 days shorter.

The first measurable snow (0.1 inch or more) in Princeton usually arrives around December 1, and the last of the season around April 8. Those are the middle dates across the winters of 1991–2020 at Montello, WI, 9.8 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 25 days after the last snow.

ZIP 54968 is 10 miles from Montello, WI, which stands at 786 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 53949 (Montello). The 2023 USDA Plant Hardiness Zone Map lists ZIP 54968 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.