U.S. Frost Dates by Weather Station

NOAA station USC00455946 · Washington

Frost Dates for Northport, WA

NOAA weather station Northport (USC00455946), Washington · elevation 1497 ft (456 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 850% chance of a frost after it
  • Typical first fall frostOctober 150% chance of a frost before it
  • Frost-free season143 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Northport, WASpring: a frost after April 27 in 9 years out of 10, after May 8 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before October 1 in half of the years, before October 14 in 9 years out of 10. Typical frost-free season: 143 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 8First frost ~Oct 1Frost season at Northport, WASpring: a frost after April 27 in 9 years out of 10, after May 8 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before October 1 in half of the years, before October 14 in 9 years out of 10. Typical frost-free season: 143 days.JFMAMJJASONDLast frost ~May 8First frost ~Oct 1
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 26September 15
50% (typical)May 8October 1
90% (likely)April 27October 14
Frost-free season (32°F, 50% chance)
143 days
Hard frost (28°F), last in spring, 50% chance after
April 26
Hard frost (28°F), first in fall, 50% chance before
October 13

The last 15 years (2006–2020 normals)

Typical last frost May 2 (6 days earlier than the 30-year normal), typical first fall frost October 12 (11 days later). Frost-free season 160 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 Northport: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 19, 30% May 14, 40% May 11, 50% May 8, 60% May 5, 70% May 2, 80% April 30, 90% April 27. Observed last spring frost in recent years: 2021 May 21, 2022 May 22, 2023 April 23, 2024 May 30, 2025 May 6, 2026 May 17.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 8Apr 272021: May 212022: May 222023: April 232024: May 302025: May 62026: May 17Fall at Northport: chance of a frost before this dateFall, chance of a frost before the date: 10% September 15, 20% September 21, 30% September 25, 40% September 28, 50% October 1, 60% October 3, 70% October 5, 80% October 9, 90% October 14. Observed first fall frost in recent years: 2021 September 16, 2022 October 27, 2023 October 26, 2024 September 30, 2025 October 5.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Nov 1Sep 15Oct 1Oct 142021: September 162022: October 272023: October 262024: September 302025: October 5
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
2021May 21September 16
2022May 22October 27
2023April 23October 26
2024May 30September 30
2025May 6October 5
2026May 17season not over yet

What these dates mean

The 143 days between the 32 °F 50 % dates of May 8 and October 1 define the span in which a light frost is less likely than not for Northport. The 50 % date, May 8, marks the point at which a light frost is equally likely to occur later as not, and the 50 % date, October 1, marks the point at which a light frost is equally likely to occur earlier as not.

For a cautious spring plan the 10 % chance date of May 26 is used, while a cautious fall plan relies on the 10 % chance date of September 15. These dates give the lowest risk for setting out or finishing tender crops, whereas the 90 % chance dates of April 27 and October 14 represent gambles.

Hard frosts at 28 °F, such as those indicated by the median hard-frost dates of April 26 and October 13, can injure plants more severely than the lighter 32 °F 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 26" 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 15" 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 Northport, WANumbered nearest stations: 1 — Boundary Dam, WA — 23 mi; 2 — Chewelah, WA — 43 mi; 3 — Republic, WA — 45 mi; 4 — Priest River, ID — 59 mi; 5 — Bonners Ferry, ID — 71 mi.WAID25 mi · 40 km1. Boundary Dam, WA — 23 mi12. Chewelah, WA — 43 mi23. Republic, WA — 45 mi34. Priest River, ID — 59 mi45. Bonners Ferry, ID — 71 mi5
  1. Boundary Dam, WA 23 mi (36 km)
  2. Chewelah, WA 43 mi (70 km)
  3. Republic, WA 45 mi (72 km)
  4. Priest River, ID 59 mi (95 km)
  5. Bonners Ferry, ID 71 mi (114 km)

Sources

* Hardiness zone 6b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 48.8994, -117.8289.