Frost Dates for 53204 — Milwaukee, Wisconsin

Half of springs at West Allis, 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 22 in half of years, as early as October 7 one year in ten, and holds off past November 3 one year in ten. A hard freeze of 28°F follows 10 days later, around November 1; 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 177 days in a typical year, longer than at 91% of the 182 Wisconsin stations; it reaches 197 days one year in ten and falls short of 158 one year in ten. On average 133 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 10. Severe cold of 16°F or below comes every winter, usually between November 29 and March 13.

July is the warmest month at West Allis, WI, averaging 85°F by day and 63°F at night; January is the coldest at 31°F and 15°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 3,001 growing degree days a year (base 50°F), more than at 97% of the 182 Wisconsin stations. 31% of them (942) have built up by the end of June, and July adds the most, 741. Precipitation totals 39.3 inches a year, most in June (5.0") and least in January (2.2"); May to September bring 53% of it.

The nearest other station, Milwaukee Mitchell Airport, WI, 4 miles south of Milwaukee, has a last frost 7 days earlier (April 19), a first frost 7 days later (October 29), a season 15 days longer.

The first measurable snow (0.1 inch or more) in Milwaukee usually arrives around November 13, and the last of the season around April 13. Those are the middle dates across the winters of 1991–2020 at Milwaukee Mitchell Airport, WI, 4.5 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 13 days after the last snow.

ZIP 53204 is 4 miles from West Allis, WI, which stands at 723 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 11 other ZIP codes share the station; its figures are presented in full for 53215 (Milwaukee). The 2023 USDA Plant Hardiness Zone Map lists ZIP 53204 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.