U.S. Frost Dates by Weather Station

NOAA station USC00451484 · Washington

Frost Dates for Clearbrook, WA

NOAA weather station Clearbrook (USC00451484), Washington · elevation 64 ft (20 m) · hardiness zone 8a*

  • Lower-risk planting dateafter May 5only 1 spring in 10 still has a frost later
  • Typical last frostApril 1850% chance of a frost after it
  • Typical first fall frostOctober 1850% chance of a frost before it
  • Frost-free season185 daystypical year, 32°F
  • Hardiness zone8acalculated*

The year at a glance

Frost season at Clearbrook, WASpring: a frost after March 27 in 9 years out of 10, after April 18 in half of the years, after May 5 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 18 in half of the years, before November 8 in 9 years out of 10. Typical frost-free season: 185 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 18First frost ~Oct 18Frost season at Clearbrook, WASpring: a frost after March 27 in 9 years out of 10, after April 18 in half of the years, after May 5 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 18 in half of the years, before November 8 in 9 years out of 10. Typical frost-free season: 185 days.JFMAMJJASONDLast frost ~Apr 18First frost ~Oct 18
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 5September 28
50% (typical)April 18October 18
90% (likely)March 27November 8
Frost-free season (32°F, 50% chance)
185 days
Hard frost (28°F), last in spring, 50% chance after
March 18
Hard frost (28°F), first in fall, 50% chance before
November 7

The last 15 years (2006–2020 normals)

Typical last frost April 15 (3 days earlier than the 30-year normal), typical first fall frost October 16 (2 days earlier). Frost-free season 187 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 Clearbrook: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 5, 20% May 1, 30% April 27, 40% April 22, 50% April 18, 60% April 14, 70% April 8, 80% April 3, 90% March 27. Observed last spring frost in recent years: 2021 April 12, 2022 April 16, 2023 April 21, 2024 April 10, 2025 April 23, 2026 April 9.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 5Apr 18Mar 272021: April 122022: April 162023: April 212024: April 102025: April 232026: April 9Fall at Clearbrook: chance of a frost before this dateFall, chance of a frost before the date: 10% September 28, 20% October 4, 30% October 8, 40% October 13, 50% October 18, 60% October 22, 70% October 28, 80% November 1, 90% November 8. Observed first fall frost in recent years: 2021 October 12, 2022 October 23, 2023 October 26, 2024 December 2, 2025 November 30.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Dec 1Sep 28Oct 18Nov 82021: October 122022: October 232023: October 262024: December 22025: 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 12October 12
2022April 16October 23
2023April 21October 26
2024April 10December 2
2025April 23November 30
2026April 9season not over yet

What these dates mean

Setting out tender crops on March 27 in Clearbrook is a gamble, because there is a 90 % chance of a light frost later than that date. The cautious date for spring planting is May 5, when only a 10 % chance of a later frost remains.

The 50% light-frost date in spring is April 18, indicating an even odds of a frost occurring later, and the median hard-frost date in spring is March 18. In fall the 50% light-frost date is October 18 and the median hard-frost date is November 7, each marking the point of equal likelihood of a frost having arrived earlier.

For finishing tender crops the cautious fall date is September 28, with only a 10 % chance that a frost has already arrived; waiting until November 8 would be a gamble with a 90 % chance of an earlier frost. A hard frost at 28 °F can damage plants more seriously than a light frost at 32 °F because the lower temperature freezes tissue more deeply.

How to read the probabilities

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

  • Spring: "10% after May 5" 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 September 28" 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 Clearbrook, WANumbered nearest stations: 1 — Bellingham (Airport), WA — 15 mi; 2 — near Bellingham, WA — 19 mi; 3 — Upper Baker Dam, WA — 36 mi; 4 — Concrete PPL Fish Station, WA — 40 mi; 5 — Newhalem, WA — 53 mi.25 mi · 40 km1. Bellingham (Airport), WA — 15 mi12. near Bellingham, WA — 19 mi23. Upper Baker Dam, WA — 36 mi34. Concrete PPL Fish Station, WA — 40 mi45. Newhalem, WA — 53 mi5
  1. Bellingham (Airport), WA 15 mi (25 km)
  2. near Bellingham, WA 19 mi (31 km)
  3. Upper Baker Dam, WA 36 mi (58 km)
  4. Concrete PPL Fish Station, WA 40 mi (64 km)
  5. Newhalem, WA 53 mi (86 km)

Sources

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

Station coordinates: 48.9672, -122.3292.