U.S. Frost Dates by Weather Station

NOAA station USW00024229 · Oregon

Frost Dates for Portland, OR

NOAA weather station Portland International Airport (USW00024229), Oregon · elevation 19 ft (6 m) · hardiness zone 9a*

  • Lower-risk planting dateafter April 1only 1 spring in 10 still has a frost later
  • Typical last frostMarch 1350% chance of a frost after it
  • Typical first fall frostNovember 1950% chance of a frost before it
  • Frost-free season247 daystypical year, 32°F
  • Hardiness zone9acalculated*

The year at a glance

Frost season at Portland, ORSpring: a frost after February 22 in 9 years out of 10, after March 13 in half of the years, after April 1 in 1 year out of 10. Fall: the first frost comes before October 29 in 1 year out of 10, before November 19 in half of the years, before December 10 in 9 years out of 10. Typical frost-free season: 247 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Mar 13First frost ~Nov 19Frost season at Portland, ORSpring: a frost after February 22 in 9 years out of 10, after March 13 in half of the years, after April 1 in 1 year out of 10. Fall: the first frost comes before October 29 in 1 year out of 10, before November 19 in half of the years, before December 10 in 9 years out of 10. Typical frost-free season: 247 days.JFMAMJJASONDLast frost ~Mar 13First frost ~Nov 19
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.Today

Frost dates (32°F)

Probability of frost, based on 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 1October 29
50% (typical)March 13November 19
90% (likely)February 22December 10
Frost-free season (32°F, 50% chance)
247 days
Hard frost (28°F), last in spring, 50% chance after
February 16
Hard frost (28°F), first in fall, 50% chance before
December 5

The last 15 years (2006–2020 normals)

Typical last frost March 15 (2 days later than the 30-year normal), typical first fall frost November 20 (1 day later). Frost-free season 251 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 Portland: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 1, 20% March 26, 30% March 21, 40% March 17, 50% March 13, 60% March 9, 70% March 6, 80% February 28, 90% February 22. Observed last spring frost in recent years: 2021 April 11, 2022 March 10, 2023 March 16, 2024 March 8, 2025 February 14, 2026 March 26.Spring: last frostChance of a frost after this date10%50%90%Mar 1Apr 1Apr 1Mar 13Feb 222021: April 112022: March 102023: March 162024: March 82025: February 142026: March 26Fall at Portland: chance of a frost before this dateFall, chance of a frost before the date: 10% October 29, 20% November 5, 30% November 11, 40% November 14, 50% November 19, 60% November 23, 70% November 27, 80% December 2, 90% December 10. Observed first fall frost in recent years: 2021 December 26, 2022 November 13, 2023 October 28, 2024 November 30, 2025 December 1.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Jan 1Oct 29Nov 19Dec 102021: December 262022: November 132023: October 282024: November 302025: December 1
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 11December 26
2022March 10November 13
2023March 16October 28
2024March 8November 30
2025February 14December 1
2026March 26season not over yet

What these dates mean

The cautious fall date for finishing the harvest in Portland is October 29, when there is only a 10 % chance that a light frost has already arrived.

For light frost, the 50% date is March 13 in spring, meaning a gardener faces a 50 % chance of a frost later than that date, and the 50% date is November 19 in fall, indicating a 50 % chance of a frost earlier than that date. The hard-frost 50% dates are February 16 in spring and December 5 in fall; these mark the point at which a 28 °F frost is equally likely to have occurred.

A cautious planting schedule uses the April 1 light-frost date in spring and the October 29 date in fall for tender crops. Hard frosts matter more because 28 °F can injure plants that would survive a 32 °F light frost.

How to read the probabilities

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

  • Spring: "10% after April 1" 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 29" 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 Portland, ORNumbered nearest stations: 1 — Vancouver, WA — 6 mi; 2 — Battle Ground, WA — 13 mi; 3 — near Sandy, OR — 24 mi; 4 — Forest Grove, OR — 25 mi; 5 — Estacada, OR — 26 mi.ORWA25 mi · 40 km1. Vancouver, WA — 6 mi12. Battle Ground, WA — 13 mi23. near Sandy, OR — 24 mi34. Forest Grove, OR — 25 mi45. Estacada, OR — 26 mi5
  1. Vancouver, WA 6 mi (10 km)
  2. Battle Ground, WA 13 mi (21 km)
  3. near Sandy, OR 24 mi (38 km)
  4. Forest Grove, OR 25 mi (40 km)
  5. Estacada, OR 26 mi (42 km)

Sources

* Hardiness zone 9a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 45.5908, -122.6003.