Frost Dates for 54234 — Sister Bay, Wisconsin

Half of springs at Ephraim 1NE-Wwtp, WI see their last 32°F night by May 14; only one in ten is past it by April 28, and one in ten still has one after May 28. Planting tender crops after May 20 leaves a 30% risk of a frost on them, after May 23 20%, and after May 28 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 18 in half of years, as early as October 1 one year in ten, and holds off past November 3 one year in ten. A hard freeze of 28°F follows 14 days later, around November 1; in spring the one-in-ten date for 28°F is May 17, 11 days before the 32°F one. The freeze-free season lasts 155 days in a typical year, shorter than at 51% of the 182 Wisconsin stations; it reaches 177 days one year in ten and falls short of 134 one year in ten. On average 155 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 26, and return around October 4. Severe cold of 16°F or below comes every winter, usually between December 1 and March 31.

July is the warmest month at Ephraim 1NE-Wwtp, WI, averaging 80°F by day and 58°F at night; January is the coldest at 27°F and 12°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 85% of years.

Warmth for growing adds up to 2,108 growing degree days a year (base 50°F), fewer than at 82% of the 182 Wisconsin stations. 27% of them (574) have built up by the end of June, and July adds the most, 579. Precipitation totals 31.1 inches a year, most in October (3.6") and least in February (1.1"); May to September bring 52% of it.

The nearest other station, Sturgeon Bay Exp Farm, WI, 24 miles southwest of Sister Bay, has a last frost 6 days earlier (May 8), a first frost 5 days earlier (October 13), a season 2 days longer.

The first measurable snow (0.1 inch or more) in Sister Bay usually arrives around November 23, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Washington Is, WI, 16.1 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 32 days after the last snow.

ZIP 54234 is 2 miles from Ephraim 1NE-Wwtp, WI, which stands at 733 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 54234 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.