U.S. Frost Dates by Weather Station

NOAA station USC00451783 · Washington

Frost Dates for Coupeville, WA

NOAA weather station Coupeville 1 S (USC00451783), Washington · elevation 50 ft (15 m) · hardiness zone 8b*

  • Lower-risk planting dateafter April 3only 1 spring in 10 still has a frost later
  • Typical last frostMarch 1750% chance of a frost after it
  • Typical first fall frostNovember 1150% chance of a frost before it
  • Frost-free season237 daystypical year, 32°F
  • Hardiness zone8bcalculated*

The year at a glance

Frost season at Coupeville, WASpring: a frost after February 24 in 9 years out of 10, after March 17 in half of the years, after April 3 in 1 year out of 10. Fall: the first frost comes before October 21 in 1 year out of 10, before November 11 in half of the years, before December 1 in 9 years out of 10. Typical frost-free season: 237 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Mar 17First frost ~Nov 11Frost season at Coupeville, WASpring: a frost after February 24 in 9 years out of 10, after March 17 in half of the years, after April 3 in 1 year out of 10. Fall: the first frost comes before October 21 in 1 year out of 10, before November 11 in half of the years, before December 1 in 9 years out of 10. Typical frost-free season: 237 days.JFMAMJJASONDLast frost ~Mar 17First frost ~Nov 11
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)April 3October 21
50% (typical)March 17November 11
90% (likely)February 24December 1
Frost-free season (32°F, 50% chance)
237 days
Hard frost (28°F), last in spring, 50% chance after
February 21
Hard frost (28°F), first in fall, 50% chance before
November 28

The last 15 years (2006–2020 normals)

Typical last frost March 18 (1 day later than the 30-year normal), typical first fall frost November 13 (2 days later). Frost-free season 240 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 Coupeville: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 3, 20% March 30, 30% March 26, 40% March 21, 50% March 17, 60% March 11, 70% March 7, 80% March 2, 90% February 24.Spring: last frostChance of a frost after this date10%50%90%Mar 1Apr 1Apr 3Mar 17Feb 24Fall at Coupeville: chance of a frost before this dateFall, chance of a frost before the date: 10% October 21, 20% October 30, 30% November 3, 40% November 7, 50% November 11, 60% November 16, 70% November 20, 80% November 25, 90% December 1.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 21Nov 11Dec 1
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.

What these dates mean

There are 237 days between the 32 °F 50% dates, March 17 and November 11, and within that interval Coupeville gardeners can expect a season bounded by roughly equal odds of a light frost. The 50% dates mark the point at which the chance of a light frost is exactly fifty percent, neither favoring earlier nor later occurrence.

The cautious spring date for tender crops is April 3, when there is only a ten-percent chance of a light frost later; planting before February 24 would be a gamble with a ninety-percent chance of frost. In the fall the cautious date is October 21, offering a ten-percent chance that a light frost has arrived earlier, while waiting until December 1 would involve a ninety-percent risk of frost.

The hard-frost 50% dates are February 21 in spring and November 28 in fall. A hard frost at 28 °F can damage plants that survive a light frost at 32 °F, making it the more critical threshold.

How to read the probabilities

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

  • Spring: "10% after April 3" 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 October 21" 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 Coupeville, WANumbered nearest stations: 1 — Sequim, WA — 19 mi; 2 — Everett, WA — 28 mi; 3 — near Bellingham, WA — 36 mi; 4 — Bellingham (Airport), WA — 41 mi; 5 — near Kirkland, WA — 41 mi.25 mi · 40 km1. Sequim, WA — 19 mi12. Everett, WA — 28 mi23. near Bellingham, WA — 36 mi34. Bellingham (Airport), WA — 41 mi45. near Kirkland, WA — 41 mi5
  1. Sequim, WA 19 mi (31 km)
  2. Everett, WA 28 mi (45 km)
  3. near Bellingham, WA 36 mi (58 km)
  4. Bellingham (Airport), WA 41 mi (66 km)
  5. near Kirkland, WA 41 mi (66 km)

Sources

* Hardiness zone 8b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 48.2072, -122.6914.