U.S. Frost Dates by Weather Station

NOAA station USW00024233 · Washington

Frost Dates for Seattle (Seattle-Tacoma Airport), WA

NOAA weather station Seattle Tacoma International Airport (USW00024233), Washington · elevation 370 ft (113 m) · hardiness zone 9a*

  • Lower-risk planting dateafter March 23only 1 spring in 10 still has a frost later
  • Typical last frostMarch 250% chance of a frost after it
  • Typical first fall frostNovember 2350% chance of a frost before it
  • Frost-free season266 daystypical year, 32°F
  • Hardiness zone9acalculated*

The year at a glance

Frost season at Seattle (Seattle-Tacoma Airport), WASpring: a frost after February 5 in 9 years out of 10, after March 2 in half of the years, after March 23 in 1 year out of 10. Fall: the first frost comes before November 6 in 1 year out of 10, before November 23 in half of the years, before December 15 in 9 years out of 10. Typical frost-free season: 266 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Mar 2First frost ~Nov 23Frost season at Seattle (Seattle-Tacoma Airport), WASpring: a frost after February 5 in 9 years out of 10, after March 2 in half of the years, after March 23 in 1 year out of 10. Fall: the first frost comes before November 6 in 1 year out of 10, before November 23 in half of the years, before December 15 in 9 years out of 10. Typical frost-free season: 266 days.JFMAMJJASONDLast frost ~Mar 2First frost ~Nov 23
frost likely chance fading 90% → 10% frost-free in a typical yearThe year at a glance. Blue: frost is likely; the gradient fades as the chance drops from 90% to 10%; green: the frost-free part of a typical year.

Frost dates (32°F)

Probability of frost, based on 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)March 23November 6
50% (typical)March 2November 23
90% (likely)February 5December 15
Frost-free season (32°F, 50% chance)
266 days
Hard frost (28°F), last in spring, 50% chance after
February 4
Hard frost (28°F), first in fall, 50% chance before
December 10

The last 15 years (2006–2020 normals)

Typical last frost March 5 (3 days later than the 30-year normal), typical first fall frost November 24 (1 day later). Frost-free season 264 days.

A shorter, more recent NOAA period. The 30-year normals above remain the main reference: 15 years carry more year-to-year noise.

Add these dates to your calendar Yearly reminders for the typical last frost, the lower-risk planting date and the typical first fall frost (.ics).

How the chance of frost changes with the date

Spring at Seattle (Seattle-Tacoma Airport): chance of a frost after this dateSpring, chance of a frost after the date: 10% March 23, 20% March 16, 30% March 12, 40% March 7, 50% March 2, 60% February 27, 70% February 22, 80% February 16, 90% February 5. Observed last spring frost in recent years: 2021 March 8, 2022 April 13, 2023 March 27, 2024 March 7, 2025 February 14, 2026 March 30.Spring: last frostChance of a frost after this date10%50%90%Feb 1Mar 1Apr 1Mar 23Mar 2Feb 52021: March 82022: April 132023: March 272024: March 72025: February 142026: March 30Fall at Seattle (Seattle-Tacoma Airport): chance of a frost before this dateFall, chance of a frost before the date: 10% November 6, 20% November 11, 30% November 14, 40% November 18, 50% November 23, 60% November 28, 70% December 2, 80% December 7, 90% December 15. Observed first fall frost in recent years: 2021 November 17, 2022 November 9, 2023 October 29, 2024 November 28, 2025 November 30.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Nov 6Nov 23Dec 152021: November 172022: November 92023: October 292024: November 282025: November 30
Two charts, because spring and fall answer different questions: in spring, the chance that a frost still comes after a date; in fall, the chance that the first frost has already come before it. NOAA publishes these odds from 10% to 90%, so the lines stop there. ◆ marks the actual date in each recent year.

What actually happened in recent years

Observed dates of the last spring and first fall frost (32°F) at this station; ◆ marks them on the charts above
YearLast spring frostFirst fall frost
2021March 8November 17
2022April 13November 9
2023March 27October 29
2024March 7November 28
2025February 14November 30
2026March 30season not over yet

What these dates mean

Setting out tender crops on the early spring date, February 5, carries a 90 % chance of a frost later than that date, making it a high-risk choice for Seattle-Tacoma Airport growers.

The cautious spring date for tender crops is March 23, which has only a 10 % chance of a later frost, while the cautious fall date to finish harvesting tender crops is November 6, with a 10 % chance of an earlier frost. The 50 % dates are March 2 for spring and November 23 for fall; they mark the median odds of a frost occurring in the historical record. Hard-frost median dates are February 4 in spring and December 10 in fall.

Because a hard frost at 28 °F can injure plant tissue that tolerates a light frost at 32 °F, it represents a more severe threat to tender crops.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after March 23" means that in about one spring out of ten a frost still happens after that date. The 90% date is the earliest: a frost after it happens in most years.
  • Fall: "10% before November 6" means that in about one fall out of ten the first frost arrives before that date.
  • 50% is the typical date: half of the years are earlier, half are later.
  • A light frost (32°F) damages tender plants; a hard frost (28°F) also stops most hardy vegetables.

Nearby weather stations

Map of weather stations near Seattle (Seattle-Tacoma Airport), WANumbered nearest stations: 1 — Kent, WA — 4 mi; 2 — near Tacoma, WA — 14 mi; 3 — near Kirkland, WA — 17 mi; 4 — Palmer, WA — 24 mi; 5 — near Wilderness Rim, WA — 26 mi.25 mi · 40 km1. Kent, WA — 4 mi12. near Tacoma, WA — 14 mi23. near Kirkland, WA — 17 mi34. Palmer, WA — 24 mi45. near Wilderness Rim, WA — 26 mi5
  1. Kent, WA 4 mi (6 km)
  2. near Tacoma, WA 14 mi (23 km)
  3. near Kirkland, WA 17 mi (27 km)
  4. Palmer, WA 24 mi (38 km)
  5. near Wilderness Rim, WA 26 mi (42 km)

Sources

* Hardiness zone 9a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 47.4444, -122.3139.