U.S. Frost Dates by Weather Station

NOAA station USC00458715 · Washington

Frost Dates for Upper Baker Dam, WA

NOAA weather station Upper Baker Dam (USC00458715), Washington · elevation 690 ft (210 m) · hardiness zone 8a*

  • Lower-risk planting dateafter May 9only 1 spring in 10 still has a frost later
  • Typical last frostApril 2450% chance of a frost after it
  • Typical first fall frostOctober 2950% chance of a frost before it
  • Frost-free season190 daystypical year, 32°F
  • Hardiness zone8acalculated*

The year at a glance

Frost season at Upper Baker Dam, WASpring: a frost after April 4 in 9 years out of 10, after April 24 in half of the years, after May 9 in 1 year out of 10. Fall: the first frost comes before October 12 in 1 year out of 10, before October 29 in half of the years, before November 17 in 9 years out of 10. Typical frost-free season: 190 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 24First frost ~Oct 29Frost season at Upper Baker Dam, WASpring: a frost after April 4 in 9 years out of 10, after April 24 in half of the years, after May 9 in 1 year out of 10. Fall: the first frost comes before October 12 in 1 year out of 10, before October 29 in half of the years, before November 17 in 9 years out of 10. Typical frost-free season: 190 days.JFMAMJJASONDLast frost ~Apr 24First frost ~Oct 29
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 9October 12
50% (typical)April 24October 29
90% (likely)April 4November 17
Frost-free season (32°F, 50% chance)
190 days
Hard frost (28°F), last in spring, 50% chance after
March 28
Hard frost (28°F), first in fall, 50% chance before
November 17

The last 15 years (2006–2020 normals)

Typical last frost April 21 (3 days earlier than the 30-year normal), typical first fall frost October 29. 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 Upper Baker Dam: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 9, 20% May 4, 30% April 30, 40% April 27, 50% April 24, 60% April 19, 70% April 15, 80% April 11, 90% April 4. Observed last spring frost in recent years: 2021 April 15, 2022 April 21, 2023 April 15, 2025 April 18, 2026 April 26.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 9Apr 24Apr 42021: April 152022: April 212023: April 152025: April 182026: April 26Fall at Upper Baker Dam: chance of a frost before this dateFall, chance of a frost before the date: 10% October 12, 20% October 18, 30% October 22, 40% October 25, 50% October 29, 60% November 1, 70% November 5, 80% November 10, 90% November 17. Observed first fall frost in recent years: 2021 October 30, 2022 November 3, 2023 October 26, 2024 November 18, 2025 November 30.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Dec 1Oct 12Oct 29Nov 172021: October 302022: November 32023: October 262024: November 182025: 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 15October 30
2022April 21November 3
2023April 15October 26
2024incomplete recordNovember 18
2025April 18November 30
2026April 26season not over yet

What these dates mean

The cautious fall date for finishing the harvest at Upper Baker Dam is October 12, when there is only a 10 % chance that a light frost has occurred earlier.

In spring the cautious date for setting out tender crops is May 9, which carries a 10 % chance of a light frost later, while planting on April 4 would be a gamble with a 90 % chance. The 50 % light-frost dates are April 24 and October 29, and the 50 % hard-frost dates are March 28 and November 17. These dates indicate the point at which the probability of a frost is even, not an actual frost occurrence.

Hard frosts at 28 °F matter more than light frosts at 32 °F because the lower temperature can freeze plant tissue more deeply, posing a greater risk to tender crops.

How to read the probabilities

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

  • Spring: "10% after May 9" 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 12" 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 Upper Baker Dam, WANumbered nearest stations: 1 — Concrete PPL Fish Station, WA — 8 mi; 2 — Newhalem, WA — 21 mi; 3 — Diablo Dam, WA — 25 mi; 4 — Ross Dam, WA — 29 mi; 5 — Clearbrook, WA — 36 mi.WA25 mi · 40 km1. Concrete PPL Fish Station, WA — 8 mi12. Newhalem, WA — 21 mi23. Diablo Dam, WA — 25 mi34. Ross Dam, WA — 29 mi45. Clearbrook, WA — 36 mi5
  1. Concrete PPL Fish Station, WA 8 mi (13 km)
  2. Newhalem, WA 21 mi (33 km)
  3. Diablo Dam, WA 25 mi (41 km)
  4. Ross Dam, WA 29 mi (46 km)
  5. Clearbrook, WA 36 mi (58 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: 48.6525, -121.6931.