U.S. Frost Dates by Weather Station

NOAA station USC00453826 · Washington

Frost Dates for Humptulips Salmon Hatchery, WA

NOAA weather station Humptulips Salmon Hatchery (USC00453826), Washington · elevation 140 ft (43 m) · hardiness zone 8b*

  • Lower-risk planting dateafter May 15only 1 spring in 10 still has a frost later
  • Typical last frostApril 2650% chance of a frost after it
  • Typical first fall frostOctober 2250% chance of a frost before it
  • Frost-free season180 daystypical year, 32°F
  • Hardiness zone8bcalculated*

The year at a glance

Frost season at Humptulips Salmon Hatchery, WASpring: a frost after March 31 in 9 years out of 10, after April 26 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 22 in half of the years, before November 15 in 9 years out of 10. Typical frost-free season: 180 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 26First frost ~Oct 22Frost season at Humptulips Salmon Hatchery, WASpring: a frost after March 31 in 9 years out of 10, after April 26 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 22 in half of the years, before November 15 in 9 years out of 10. Typical frost-free season: 180 days.JFMAMJJASONDLast frost ~Apr 26First frost ~Oct 22
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)May 15October 3
50% (typical)April 26October 22
90% (likely)March 31November 15
Frost-free season (32°F, 50% chance)
180 days
Hard frost (28°F), last in spring, 50% chance after
March 27
Hard frost (28°F), first in fall, 50% chance before
November 13

The last 15 years (2006–2020 normals)

Typical last frost April 15 (11 days earlier than the 30-year normal), typical first fall frost October 23 (1 day later). Frost-free season 193 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 Humptulips Salmon Hatchery: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 15, 20% May 7, 30% May 3, 40% April 30, 50% April 26, 60% April 21, 70% April 16, 80% April 9, 90% March 31. Observed last spring frost in recent years: 2021 April 15, 2022 April 28, 2023 April 6, 2024 April 23, 2025 April 23, 2026 April 18.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 15Apr 26Mar 312021: April 152022: April 282023: April 62024: April 232025: April 232026: April 18Fall at Humptulips Salmon Hatchery: chance of a frost before this dateFall, chance of a frost before the date: 10% October 3, 20% October 9, 30% October 14, 40% October 19, 50% October 22, 60% October 26, 70% October 30, 80% November 4, 90% November 15. Observed first fall frost in recent years: 2021 October 11, 2022 October 23, 2023 October 27, 2024 November 15, 2025 October 14.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 3Oct 22Nov 152021: October 112022: October 232023: October 272024: November 152025: October 14
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 15October 11
2022April 28October 23
2023April 6October 27
2024April 23November 15
2025April 23October 14
2026April 18season not over yet

What these dates mean

The 180 days between the 50% light-frost dates of April 26 and October 22 at Humptulips Salmon Hatchery frame the window in which tender crops can generally be cultivated. A 50% date marks the median point, meaning the chance of a light frost is equal on either side of that day. The hard-frost median dates are March 27 in spring and November 13 in fall, indicating when a 28 °F event becomes as likely as not.

Cautious planting in spring follows the May 15 date, which carries only a 10% chance of a light frost later, while cautious harvesting in fall uses the October 3 date, which has a 10% chance of a light frost earlier. A hard frost at 28 °F matters more than a light frost at 32 °F because the colder temperature can damage plant tissue that survives milder frosts.

How to read the probabilities

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

  • Spring: "10% after May 15" 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 3" 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 Humptulips Salmon Hatchery, WANumbered nearest stations: 1 — near Hoquiam, WA — 18 mi; 2 — Aberdeen, WA — 20 mi; 3 — Elma, WA — 32 mi; 4 — Cushman Powerhouse #2, WA — 40 mi; 5 — Raymond, WA — 42 mi.WA25 mi · 40 km1. near Hoquiam, WA — 18 mi12. Aberdeen, WA — 20 mi23. Elma, WA — 32 mi34. Cushman Powerhouse #2, WA — 40 mi45. Raymond, WA — 42 mi5
  1. near Hoquiam, WA 18 mi (29 km)
  2. Aberdeen, WA 20 mi (32 km)
  3. Elma, WA 32 mi (51 km)
  4. Cushman Powerhouse #2, WA 40 mi (64 km)
  5. Raymond, WA 42 mi (67 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: 47.2336, -123.9897.