U.S. Frost Dates by Weather Station

NOAA station USC00455840 · Washington

Frost Dates for Newhalem, WA

NOAA weather station Newhalem (USC00455840), Washington · elevation 525 ft (160 m) · hardiness zone 8b*

  • Lower-risk planting dateafter April 27only 1 spring in 10 still has a frost later
  • Typical last frostApril 250% chance of a frost after it
  • Typical first fall frostNovember 1450% chance of a frost before it
  • Frost-free season224 daystypical year, 32°F
  • Hardiness zone8bcalculated*

The year at a glance

Frost season at Newhalem, WASpring: a frost after March 9 in 9 years out of 10, after April 2 in half of the years, after April 27 in 1 year out of 10. Fall: the first frost comes before October 28 in 1 year out of 10, before November 14 in half of the years, before December 5 in 9 years out of 10. Typical frost-free season: 224 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 2First frost ~Nov 14Frost season at Newhalem, WASpring: a frost after March 9 in 9 years out of 10, after April 2 in half of the years, after April 27 in 1 year out of 10. Fall: the first frost comes before October 28 in 1 year out of 10, before November 14 in half of the years, before December 5 in 9 years out of 10. Typical frost-free season: 224 days.JFMAMJJASONDLast frost ~Apr 2First 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 27October 28
50% (typical)April 2November 14
90% (likely)March 9December 5
Frost-free season (32°F, 50% chance)
224 days
Hard frost (28°F), last in spring, 50% chance after
March 2
Hard frost (28°F), first in fall, 50% chance before
December 4

The last 15 years (2006–2020 normals)

Typical last frost April 2 (same as the 30-year normal), typical first fall frost November 16 (2 days later). Frost-free season 224 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 Newhalem: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 27, 20% April 17, 30% April 9, 40% April 5, 50% April 2, 60% March 29, 70% March 24, 80% March 18, 90% March 9. Observed last spring frost in recent years: 2021 April 12, 2022 April 13, 2023 April 15, 2024 April 18, 2025 March 18, 2026 March 31.Spring: last frostChance of a frost after this date10%50%90%Mar 1Apr 1May 1Apr 27Apr 2Mar 92021: April 122022: April 132023: April 152024: April 182025: March 182026: March 31Fall at Newhalem: chance of a frost before this dateFall, chance of a frost before the date: 10% October 28, 20% November 3, 30% November 7, 40% November 10, 50% November 14, 60% November 18, 70% November 21, 80% November 26, 90% December 5. Observed first fall frost in recent years: 2021 November 23, 2022 November 3, 2023 November 15, 2024 November 17, 2025 December 21.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 28Nov 14Dec 52021: November 232022: November 32023: November 152024: November 172025: December 21
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 23
2022April 13November 3
2023April 15November 15
2024April 18November 17
2025March 18December 21
2026March 31season not over yet

What these dates mean

October 28 marks the cautious fall date for finishing the harvest of tender crops in Newhalem, since there is only a ten percent chance that a light frost has arrived earlier.

The 50% dates are benchmarks where the odds are even. The median light-frost date, April 2, represents a fifty percent chance of a light frost later than this date, and the median hard-frost date, March 2, represents a fifty percent chance of a hard frost later than this date. In spring, the cautious date for setting out tender crops is April 27, with only a ten percent chance of a frost later; planting on March 9 carries a ninety percent gamble. In fall, the cautious date for wrapping up tender crops is October 28, with only a ten percent chance of a frost earlier; waiting until December 5 involves a ninety percent gamble.

Because a hard frost at 28 °F can injure plants that survive a light frost at 32 °F, it represents a more severe threat.

How to read the probabilities

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

  • Spring: "10% after April 27" 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 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 Newhalem, WANumbered nearest stations: 1 — Diablo Dam, WA — 5 mi; 2 — Ross Dam, WA — 9 mi; 3 — Upper Baker Dam, WA — 21 mi; 4 — Concrete PPL Fish Station, WA — 25 mi; 5 — Stehekin, WA — 33 mi.WA25 mi · 40 km1. Diablo Dam, WA — 5 mi12. Ross Dam, WA — 9 mi23. Upper Baker Dam, WA — 21 mi34. Concrete PPL Fish Station, WA — 25 mi45. Stehekin, WA — 33 mi5
  1. Diablo Dam, WA 5 mi (8 km)
  2. Ross Dam, WA 9 mi (14 km)
  3. Upper Baker Dam, WA 21 mi (33 km)
  4. Concrete PPL Fish Station, WA 25 mi (40 km)
  5. Stehekin, WA 33 mi (52 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: 48.6758, -121.2419.