Washington Frost Dates
Published: February 1, 2026 · Updated: April 23, 2026
Last Spring Frost
May 7
Zone 4b
First Fall Frost
October 1
Zone 4b
Frost-Free Season
147 days
Early May to Late October
Lawn Care Timing for Washington
Vegetable Garden Timing for Washington
Frost Dates by City in Washington
Frequently Asked Questions
What is the last frost date in Washington?
The average last spring frost in Washington (zone 4b) is May 7. Dates vary by city and elevation. Find your specific city below for exact dates.
When is it safe to plant tomatoes in Washington?
Transplant tomato seedlings outdoors after May 7 — the average last frost date for zone 4b. Start seeds indoors Early March (8 weeks before last frost). Wait 2 weeks after last frost for extra safety.
When should I overseed my lawn in Washington?
The prime overseeding window in Washington is September 1–15. This ensures 6 weeks of warm soil for germination before the first fall frost on October 1.
When should I apply winteriser in Washington?
Apply winteriser fertiliser by Late October. Your first fall frost of October 1 is the hard deadline — apply at least 2–3 weeks before.
What USDA zone is Washington?
Washington contains USDA zones 4b. Each zone has different frost dates and growing seasons. Find your city below for your specific zone.