Frost Dates for 53223 — Milwaukee, Wisconsin

Half of springs at Mt Mary College, WI see their last 32°F night by April 26; only one in ten is past it by April 12, and one in ten still has one after May 12. Planting tender crops after May 2 leaves a 30% risk of a frost on them, after May 6 20%, and after May 12 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 70% 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 2 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 12 days later, around October 30; in spring the one-in-ten date for 28°F is April 30, 12 days before the 32°F one. The freeze-free season lasts 173 days in a typical year, longer than at 86% of the 182 Wisconsin stations; it reaches 192 days one year in ten and falls short of 153 one year in ten. On average 134 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 8, and return around October 6. Severe cold of 16°F or below comes every winter, usually between November 27 and March 15.

July is the warmest month at Mt Mary College, WI, averaging 83°F by day and 63°F at night; January is the coldest at 30°F and 14°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 35% of years.

Warmth for growing adds up to 2,804 growing degree days a year (base 50°F), more than at 91% of the 182 Wisconsin stations. 31% of them (878) have built up by the end of June, and July adds the most, 715. Precipitation totals 33.8 inches a year, most in June (4.8") and least in January (1.5"); May to September bring 56% of it.

The nearest other station, Germantown, WI, 9 miles northwest of Milwaukee, has a last frost 10 days later (May 6), a first frost 10 days earlier (October 8), a season 19 days shorter.

The first measurable snow (0.1 inch or more) in Milwaukee usually arrives around November 28, and the last of the season around March 31. Those are the middle dates across the winters of 1991–2020 at Mt Mary College, WI, 6.7 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 26 days after the last snow.

ZIP 53223 is 7 miles from Mt Mary College, WI, which stands at 715 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 14 other ZIP codes share the station; its figures are presented in full for 53209 (Milwaukee). The 2023 USDA Plant Hardiness Zone Map lists ZIP 53223 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.