Frost dates / Oregon / Portland

Frost dates in Portland, OR

The station on this page is PORTLAND KGW-TV, OR US (USC00356749), 2.3 miles from the city point. Population in the Census 2024 estimate is 635,749.

Zone 8bUSDA average annual extreme minimum 15°F to 20°F, from ZIP 97212 (0.6 miles from the city point used on this page).

Median last 32°F is February 25. Median first 32°F is December 1. The 50% growing-season length is 280 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%	January 24	Earlier date. A last 32°F on or after this day is common.
50%	February 25	Median.
10%	March 21	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 10	Earlier date. A first 32°F on or before this day is uncommon.
50%	December 1	Median.
90%	December 27	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%	318
50%	280
90%	245

28°F threshold

	10%	50%	90%
Last, on or after	February 26	January 31	December 21
First, on or before	November 25	December 20	January 30
Season at least	365 days	329 days	292 days

36°F threshold

	10%	50%	90%
Last, on or after	April 21	March 29	March 7
First, on or before	October 28	November 12	December 1
Season at least	258 days	227 days	200 days

Station PORTLAND KGW-TV, OR US (USC00356749). Completeness flag R, 24 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 99.7%. Freeze dates are conditional on that threshold occurring. Elevation 48.5 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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Portland, OR

Zone 8bAverage annual extreme minimum 15°F to 20°F

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

Oregon. Nearest qualified station: PORTLAND KGW-TV, OR US (USC00356749), 2.3 miles. Median last 32°F February 25. Median first 32°F December 1. The 50% growing-season length is 280 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	March 21	February 25	January 24
First 32°F on or before	November 10	December 1	December 27

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 Oregon 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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