Frost dates for Seattle, Washington
In Seattle, half of springs have had their last frost by March 8 (and 1 spring in 10 still has one after March 29), and half of falls have had their first frost by November 23, leaving about 259 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Seattle, Washington
Last spring frost
March 8
Half of springs have their last frost by this date. For a safer bet, wait until March 29: only 1 spring in 10 has a frost after that.
First fall frost
November 23
Half of falls have their first frost by this date. In 1 fall in 10 it comes by November 4.
Growing season
259 days
Frost-free days in a typical year. 9 years in 10 get at least 231.
Hardiness zone
9a
2023 USDA map: the coldest night of winter averages 20°F to 25°F. On the 2012 map it was 8b, half a zone colder. All 26 ZIP codes within about 6 miles of the city's center are in zone 9a.
Print a year planner for Seattle
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | February 13 | March 8 | March 29 |
| First frost in fall | November 4 | November 23 | December 16 |
The frost-free season between them runs 259 days in a typical year. In 1 year in 10 it is 289 days or longer, and in 1 year in 10 it is 231 days or shorter.
- Hard freeze (28°F): about 96 years in 100 have one. In those years the last typically comes on February 11 and the first on December 11. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on April 4 and first on November 5. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
In 8 springs out of 10, the last frost in Seattle comes between February 13 and March 29, a window of 44 days. That is wider than at most NOAA stations (the typical window is 31 days), so spring here is less predictable than average: lean toward the later date.
Among Washington's 154 NOAA stations with a frost every year, 96 percent have their typical last frost later than Seattle does.
Planting calendar for Seattle
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
We don't give a garlic date here. The rule we use, from the University of Minnesota Extension, counts from the first killing frost, and it works where a hard freeze comes every year before the ground freezes. Your county's extension office can tell you when to plant garlic in your climate.
| When | What to do | Why then |
|---|---|---|
| January | ||
| January 4 to February 1 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| January 18 to February 8 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| January 25 to February 8 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| February | ||
| February 1 to 15 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| February 8 to 22 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| February 8 to 22 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| February 22 to March 8 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| February 22 to March 8 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| March | ||
| March 8 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| March 22 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| March 22 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| June | ||
| June 28 to July 12 | Cabbage for fall Start seeds | set the plants out by August 16 |
| July | ||
| July 18 to August 1 | Broccoli for fall Start seeds | set the plants out by September 5 |
| August | ||
| August 27 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 31 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| September | ||
| September 1 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| September 5 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| September 6 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| September 10 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| September 20 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| September 30 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| October | ||
| October 10 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| November | ||
| November 4 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| December | ||
| December 21 to January 18 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
Want more insurance? Shift every spring date 21 days later. That plans around March 29, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Seattle Sand Point WSFO (station USW00094290), 6 miles from the center of Seattle. It sits 220 feet lower, at 60 feet above sea level. NOAA rates this station's record as standard: at least 24 of the 30 years, with gaps filled from nearby stations.
The same station also gives the frost dates for Bellevue, Kirkland, Redmond, Bothell, Bainbridge Island, Kenmore, Woodinville and Lake Forest Park.
Our ZIP code lookup matches these 34 ZIP codes to the same station, so they get the same dates: 98004, 98005, 98006, 98007, 98008, 98011, 98020, 98021, 98028, 98033, 98034, 98039, 98052, 98053, 98101, 98102, 98103, 98105, 98107, 98109, 98112, 98115, 98117, 98119, 98122, 98125, 98133, 98155, 98177, 98195, 98199, 98342, 98346, 98364. Hardiness zones are worked out separately for each ZIP code.
Nearby places
- Kent, Washington: last frost around March 2, first frost around November 23 (15 miles away)
- Everett, Washington: last frost around March 24, first frost around November 2 (25 miles away)
- Tacoma, Washington: last frost around March 11, first frost around November 21 (25 miles away)
See frost dates across Washington, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.