Frost dates / Wisconsin / West Allis

Frost dates in West Allis, WI

The station on this page is WEST ALLIS, WI US (USC00479046), 1.6 miles from the city point. Population in the Census 2024 estimate is 59,784.

Zone 5bUSDA average annual extreme minimum -15°F to -10°F, from ZIP 53227 (1 miles from the city point used on this page).

Median last 32°F is April 26. Median first 32°F is October 22. The 50% growing-season length is 177 days. The green band runs from the median last frost to the median first frost. Thin ticks mark the 10%, 50%, and 90% dates.

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Last 32°F in spring

NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.

Probability	Date	How to read it
90%	April 12	Earlier date. A last 32°F on or after this day is common.
50%	April 26	Median.
10%	May 12	Later date. A last 32°F on or after this day is uncommon.

First 32°F in fall

NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.

Probability	Date	How to read it
10%	October 7	Earlier date. A first 32°F on or before this day is uncommon.
50%	October 22	Median.
90%	November 3	Later date. A first 32°F on or before this day is common.

32°F growing-season length

Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.

Probability the season is at least this long	Days
10%	197
50%	177
90%	158

28°F threshold

	10%	50%	90%
Last, on or after	April 30	April 14	April 1
First, on or before	October 19	November 1	November 14
Season at least	219 days	200 days	178 days

36°F threshold

	10%	50%	90%
Last, on or after	May 23	May 8	April 23
First, on or before	September 29	October 10	October 24
Season at least	176 days	156 days	137 days

Station WEST ALLIS, WI US (USC00479046). Completeness flag R, 11 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 220.4 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

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West Allis, WI

Zone 5bAverage annual extreme minimum -15°F to -10°F

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Wisconsin. Nearest qualified station: WEST ALLIS, WI US (USC00479046), 1.6 miles. Median last 32°F April 26. Median first 32°F October 22. The 50% growing-season length is 177 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	May 12	April 26	April 12
First 32°F on or before	October 7	October 22	November 3

Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.

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Planting calendar

Frost dates for Wisconsin are above. Planting windows appear for states with a cited extension guide. The fall and seed tools use the numbers you enter and the station dates.

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