Frost dates / Wisconsin / Waukesha

Frost dates in Waukesha, WI

The station on this page is WAUKESHA WWTP, WI US (USC00478937), 0.3 miles from the city point. Population in the Census 2024 estimate is 71,461.

Zone 5bUSDA average annual extreme minimum -15°F to -10°F, from ZIP 53186 (2.2 miles from the city point used on this page).

Median last 32°F is May 1. Median first 32°F is October 13. The 50% growing-season length is 162 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 18	Earlier date. A last 32°F on or after this day is common.
50%	May 1	Median.
10%	May 18	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%	September 29	Earlier date. A first 32°F on or before this day is uncommon.
50%	October 13	Median.
90%	October 25	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%	183
50%	162
90%	144

28°F threshold

	10%	50%	90%
Last, on or after	May 5	April 19	April 6
First, on or before	October 8	October 23	November 6
Season at least	205 days	185 days	164 days

36°F threshold

	10%	50%	90%
Last, on or after	May 29	May 13	April 29
First, on or before	September 20	October 2	October 15
Season at least	159 days	141 days	123 days

Station WAUKESHA WWTP, WI US (USC00478937). Completeness flag R, 21 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 240.5 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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Waukesha, 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: WAUKESHA WWTP, WI US (USC00478937), 0.3 miles. Median last 32°F May 1. Median first 32°F October 13. The 50% growing-season length is 162 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	May 18	May 1	April 18
First 32°F on or before	September 29	October 13	October 25

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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