Frost dates / Washington / Burien

Frost dates in Burien, WA

The station on this page is SEATTLE TACOMA INTL AP, WA US (USW00024233), 2.6 miles from the city point. Population in the Census 2024 estimate is 52,046.

Zone 9aUSDA average annual extreme minimum 20°F to 25°F, from ZIP 98166 (1.7 miles from the city point used on this page).

Median last 32°F is March 2. Median first 32°F is November 23. The 50% growing-season length is 266 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%	February 5	Earlier date. A last 32°F on or after this day is common.
50%	March 2	Median.
10%	March 23	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%	November 6	Earlier date. A first 32°F on or before this day is uncommon.
50%	November 23	Median.
90%	December 15	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%	298
50%	266
90%	239

28°F threshold

	10%	50%	90%
Last, on or after	February 28	February 4	December 20
First, on or before	November 17	December 10	January 16
Season at least	352 days	315 days	277 days

36°F threshold

	10%	50%	90%
Last, on or after	April 21	March 31	March 13
First, on or before	October 24	November 7	November 23
Season at least	244 days	219 days	195 days

Station SEATTLE TACOMA INTL AP, WA US (USW00024233). Completeness flag S, 26 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 112.8 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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Burien, WA

Zone 9aAverage annual extreme minimum 20°F to 25°F

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

Washington. Nearest qualified station: SEATTLE TACOMA INTL AP, WA US (USW00024233), 2.6 miles. Median last 32°F March 2. Median first 32°F November 23. The 50% growing-season length is 266 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	March 23	March 2	February 5
First 32°F on or before	November 6	November 23	December 15

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 Washington 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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