White Harbor Labs › Frost Dates › States › Washington
Frost Dates in Washington
First and last frost dates across Washington, computed from 102 NOAA weather stations (1991–2020 climate normals). Your exact date depends on your city and microclimate — use the ZIP lookup on the main tool for a station-specific answer.
Last spring frost
Apr 25
statewide median · range Feb 26–Jun 6
First fall frost
Oct 17
statewide median · range Sep 10–Nov 29
Growing season
177 days
median · range 94–276
Stations used
102
NOAA 1991–2020 normals
Frost dates by city
Median dates from the nearest NOAA station to each city. The "cautious" date is the 10% spring value — planting after it means only a ~10% chance of a later frost.
| City | Nearest station | Last spring frost | First fall frost | Growing season | Safe transplant |
|---|---|---|---|---|---|
| Seattle | Seattle Boeing Fld · 4 mi | Mar 13 (cautious: Apr 1) | Nov 17 | 247 days | Mar 27 |
| Spokane | Spokane Intl Ap · 5 mi | Apr 26 (cautious: May 10) | Oct 12 | 168 days | May 10 |
| Tacoma | Tacoma #1 · 1 mi | Mar 8 (cautious: Mar 31) | Nov 14 | 250 days | Mar 22 |
How frost varies across Washington
Spring frost timing spans about 100 days across the state. Olga in northwestern Washington typically sees its last spring frost around February 26, while Davenport in eastern Washington doesn't clear frost until about June 6. Within any city, low spots and valleys run colder than the station average; areas near buildings and pavement run warmer.
When to plant in Washington
As a rule of thumb, cool-season crops (lettuce, peas, spinach) can go in 2–4 weeks before your last spring frost; warm-season transplants (tomatoes, peppers) should wait about 2 weeks after it — around May 9 for the statewide median. Check your city's row above rather than the statewide median: a 100-day statewide spread makes the city-level date the one that matters.
These are climate normals (what's typical), not forecasts. For the current year, watch the 10-day forecast around your planting date.
How this is computed
Statewide medians are the median of the 102 NOAA stations' median frost dates — half the stations run earlier, half later. City rows use the nearest station with 30-year freeze records. Dates are 32°F freeze probabilities from NOAA NCEI 1991–2020 U.S. Climate Normals; nothing is estimated or interpolated.
More states
Frequently asked questions
When is the last frost date in Washington?
The statewide median last spring frost is April 25, but it ranges from February 26 to June 6 depending on where in the state you are. Use your city's row in the table above, or the ZIP lookup on the main tool, for a station-specific date.
When can I plant tomatoes outside in Washington?
Warm-season transplants like tomatoes should wait about two weeks after your last spring frost — around May 9 for the statewide median. Your city may differ by weeks; check the "safe transplant" column in the city table.
How long is the growing season in Washington?
The median growing season across 102 NOAA stations is 177 days, ranging from 94 to 276 days by location.
Why do frost dates vary so much within Washington?
Frost timing follows latitude, elevation, and local terrain. Across Washington, last spring frost dates span about 100 days — from around February 26 near Olga to June 6 near Davenport. Microclimates (low spots, valleys, urban heat) shift dates further at the garden level.
Where does this data come from?
All frost dates are computed from the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals freeze data (public domain), using each station's 32°F freeze probability statistics. No dates are estimated or interpolated.