Seattle, WA Frost Dates: Last Spring and First Fall Frost

In a typical year the final freeze of spring reaches Seattle around March 8, and the first freeze of autumn returns around November 23. NOAA's normals call the frost-free stretch between them 259 days long.

Dates at even odds leave half of all years unprotected. The safer pair for Seattle is March 29 in spring, which only one year in ten passes, and November 4 in fall, which one year in ten arrives before. Compared with the 100-city median of 229 days, Seattle gets 30 days extra before frost returns.

These dates come from the NOAA weather station Seattle Sand Pt Wsfo (ID USW00094290), 6.5 miles north-east of the Census Bureau's internal point for Seattle, at about 60 feet above sea level.

Last spring frost in Seattle

One year in ten has a freeze on or after March 29. In nine years out of ten there is still a freeze on or after February 13, and half of years see one on or after March 8.

A span of 44 days from the 90% date to the 10% date is wide for these pages. Spring in Seattle is less predictable than in most of the 100 cities, and the late date is 21 days past the typical one.

When is the first frost in Seattle?

NOAA's early fall date for Seattle is November 4, its even-odds date is November 23 and its late date is December 16; the first freeze has come by each of them in one, five and nine years out of ten.

42 days separate the early and late fall dates, a broad band compared with most cities here, so a fall crop in Seattle should be planned against the early date, not the typical one.

The growing season in Seattle

A little more room than the middle of these pages, then, but not a different kind of garden. The gap between a typical year and a short one is 28 days, wider than for most cities on these pages. Count on 231 days, not 259 days, when a crop has little slack.

NOAA counts these days from its own simulations, so they will not equal the number of days between the two typical dates exactly. Every winter in the record reached freezing at Seattle Sand Pt Wsfo, so the dates above describe a real yearly event, not a rare one.

When a hard freeze reaches Seattle

A wide gap separates 32°F from 28°F here: the typical hard freeze arrives 18 days after the first frost in fall (December 11) and leaves 25 days before the last in spring (February 11). Frost-tolerant crops get a long extension at both ends. One spring in ten still has a 28°F night on or after March 1, and one fall in ten sees the first by November 17.

What this means for planting in Seattle

The University of New Hampshire Extension sheet times each crop from the last frost. For Seattle's typical date, March 8, that means cabbage on February 8, lettuce from February 8 to February 15, seed potatoes from February 22 to March 1, and, once the frost is behind you, peppers on March 22 and beans on or after March 8. The University of New Hampshire Extension sheet gives peas no frost count at all; sow them as soon as the soil thaws.

From the late date, March 29, every tender crop moves back 21 days; that buys protection against a spring only one year in ten brings.

Fall crops are counted back from the first frost, using NC State Extension's days to harvest plus University of Georgia Extension's harvest allowance of 18 days. In Seattle only 32 of the 34 crops in the fall planner have a last planting day in July or later, and the other 2 would have to go in before then, in spring or early summer. The slowest crop that still fits is collard greens, at 118 days, and it has to be planted by July 9 to beat the early date.

Worked example: the last day for fall broccoli in Seattle

Work through broccoli transplants for fall in Seattle. The longest days to harvest NC State Extension gives is 80 days, plus University of Georgia Extension's allowance of 18 days, for 98 days in all. Subtract that from the typical first frost on November 23 and the last day to plant is August 17; subtract it from the early date on November 4 and it is July 29.

That is 19 days between the typical and the early schedule; broccoli planted on the later of them risks a frost before harvest in one fall out of ten.

Spring is the other end of the same arithmetic: University of New Hampshire Extension sets cabbage-family transplants out two to four weeks before the last frost, which from March 8 puts cabbage out on February 8.

About the Seattle Sand Pt Wsfo station

At 6.5 miles north-east, the station is some distance from Seattle, so parts of the city may not match its record.

NOAA lists it at about 60 feet, higher than 14 and lower than 84 of the 100 stations in this set. Its completeness flag is S, which NOAA uses for a standard record.

No elevation is available for Seattle in the Census data we saved, so the station's height may or may not match your garden's. Compare nearby stations in the frost dates tool if it does not, and err toward the colder dates.

Seattle compared with nearby cities

The closest city on these pages is Tacoma, WA, 26 miles away. The next two are farther afield, so read them as a wider look at the region.

• Tacoma, WA, 26 miles to the south: last frost March 8, first frost November 14, 250 days frost-free; its last frost is nearly the same as Seattle's, and the season runs 9 days shorter.
• Portland, OR lies 145 miles south of Seattle. Typical last frost February 25, first frost December 1, 280 days between; its last frost comes 11 days before Seattle's, and the season runs 21 days longer.
• Spokane, WA lies 229 miles east of Seattle. Typical last frost April 26, first frost October 15, 170 days between; the last frost is 49 days later than in Seattle, and it has 89 days less without frost.

Take these dates further

The frost dates tool opens on this station and lists every probability date, not just the ones above. From there, the spring planting planner and fall planting planner turn the dates into crop lists for Seattle, and the hardiness zone lookup answers what will overwinter.

Every city covered is on the city frost dates index, sorted by state.

Where these numbers come from

The frost and freeze dates are NOAA's U.S. Climate Normals for 1991–2020 (doi:10.25921/4ek7-fk11), copied from the station's own record without adjustment; NOAA's documentation defines each probability. The Census Bureau's 2024 Gazetteer places Seattle on the map, and its Vintage 2024 estimates, 780,995 people here, decide which cities get a page.

The planting dates apply the count rules in University of New Hampshire Extension, NC State Extension and University of Georgia Extension to this station's dates, with nothing added. The methodology page explains how each figure is checked.

NOAA's dates say how often frost has come, not when it will. Check the forecast before planting and keep a cover on hand.