U.S. Frost Dates by Weather Station

NOAA station USC00451679 · Washington

Frost Dates for Concrete PPL Fish Station, WA

NOAA weather station Concrete PPL Fish Station (USC00451679), Washington · elevation 195 ft (59 m) · hardiness zone 8b*

  • Lower-risk planting dateafter April 19only 1 spring in 10 still has a frost later
  • Typical last frostMarch 2850% chance of a frost after it
  • Typical first fall frostNovember 1450% chance of a frost before it
  • Frost-free season229 daystypical year, 32°F
  • Hardiness zone8bcalculated*

The year at a glance

Frost season at Concrete PPL Fish Station, WASpring: a frost after March 7 in 9 years out of 10, after March 28 in half of the years, after April 19 in 1 year out of 10. Fall: the first frost comes before October 23 in 1 year out of 10, before November 14 in half of the years, before December 4 in 9 years out of 10. Typical frost-free season: 229 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Mar 28First frost ~Nov 14Frost season at Concrete PPL Fish Station, WASpring: a frost after March 7 in 9 years out of 10, after March 28 in half of the years, after April 19 in 1 year out of 10. Fall: the first frost comes before October 23 in 1 year out of 10, before November 14 in half of the years, before December 4 in 9 years out of 10. Typical frost-free season: 229 days.JFMAMJJASONDLast frost ~Mar 28First frost ~Nov 14
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 19October 23
50% (typical)March 28November 14
90% (likely)March 7December 4
Frost-free season (32°F, 50% chance)
229 days
Hard frost (28°F), last in spring, 50% chance after
February 25
Hard frost (28°F), first in fall, 50% chance before
December 2

The last 15 years (2006–2020 normals)

Typical last frost March 25 (3 days earlier than the 30-year normal), typical first fall frost November 15 (1 day later). Frost-free season 232 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 Concrete PPL Fish Station: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 19, 20% April 10, 30% April 5, 40% April 1, 50% March 28, 60% March 23, 70% March 18, 80% March 13, 90% March 7. Observed last spring frost in recent years: 2021 April 12, 2022 April 17, 2023 April 15, 2024 April 18, 2025 March 15, 2026 March 31.Spring: last frostChance of a frost after this date10%50%90%Mar 1Apr 1May 1Apr 19Mar 28Mar 72021: April 122022: April 172023: April 152024: April 182025: March 152026: March 31Fall at Concrete PPL Fish Station: chance of a frost before this dateFall, chance of a frost before the date: 10% October 23, 20% October 31, 30% November 5, 40% November 9, 50% November 14, 60% November 19, 70% November 23, 80% November 27, 90% December 4. Observed first fall frost in recent years: 2021 November 18, 2022 November 8, 2023 October 27, 2024 November 29, 2025 November 30.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 23Nov 14Dec 42021: November 182022: November 82023: October 272024: November 292025: 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
2021April 12November 18
2022April 17November 8
2023April 15October 27
2024April 18November 29
2025March 15November 30
2026March 31season not over yet

What these dates mean

April 19, the cautious spring date at Concrete PPL Fish Station, gives gardeners a window to set out tender crops with only a ten percent chance of a light frost later. The median light-frost date is March 28, indicating an even chance of a frost occurring. The median fall light-frost date is November 14, also indicating an even chance of a frost occurring. Hard-frost median dates are February 25 in spring and December 2 in fall, marking the points where a 28 °F frost is equally likely to have happened or not.

October 23, the cautious fall date, allows gardeners to finish harvesting tender crops while only a ten percent chance exists that a light frost has already arrived. A hard frost at 28 °F matters more than a light frost at 32 °F because it can cause damage that a light frost typically does not.

How to read the probabilities

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

  • Spring: "10% after April 19" 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 23" 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 Concrete PPL Fish Station, WANumbered nearest stations: 1 — Upper Baker Dam, WA — 8 mi; 2 — Newhalem, WA — 25 mi; 3 — Diablo Dam, WA — 30 mi; 4 — Ross Dam, WA — 33 mi; 5 — near Bellingham, WA — 37 mi.WA25 mi · 40 km1. Upper Baker Dam, WA — 8 mi12. Newhalem, WA — 25 mi23. Diablo Dam, WA — 30 mi34. Ross Dam, WA — 33 mi45. near Bellingham, WA — 37 mi5
  1. Upper Baker Dam, WA 8 mi (13 km)
  2. Newhalem, WA 25 mi (40 km)
  3. Diablo Dam, WA 30 mi (48 km)
  4. Ross Dam, WA 33 mi (53 km)
  5. near Bellingham, WA 37 mi (60 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: 48.5397, -121.7422.