U.S. Frost Dates by Weather Station

NOAA station USC00459238 · Washington

Frost Dates for Wilbur, WA

NOAA weather station Wilbur (USC00459238), Washington · elevation 2262 ft (690 m) · hardiness zone 6b*

  • Lower-risk planting dateafter June 22only 1 spring in 10 still has a frost later
  • Typical last frostJune 150% chance of a frost after it
  • Typical first fall frostSeptember 2250% chance of a frost before it
  • Frost-free season112 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Wilbur, WASpring: a frost after May 10 in 9 years out of 10, after June 1 in half of the years, after June 22 in 1 year out of 10. Fall: the first frost comes before September 2 in 1 year out of 10, before September 22 in half of the years, before October 5 in 9 years out of 10. Typical frost-free season: 112 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Jun 1First frost ~Sep 22Frost season at Wilbur, WASpring: a frost after May 10 in 9 years out of 10, after June 1 in half of the years, after June 22 in 1 year out of 10. Fall: the first frost comes before September 2 in 1 year out of 10, before September 22 in half of the years, before October 5 in 9 years out of 10. Typical frost-free season: 112 days.JFMAMJJASONDLast frost ~Jun 1First frost ~Sep 22
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 22September 2
50% (typical)June 1September 22
90% (likely)May 10October 5
Frost-free season (32°F, 50% chance)
112 days
Hard frost (28°F), last in spring, 50% chance after
May 8
Hard frost (28°F), first in fall, 50% chance before
October 3

The last 15 years (2006–2020 normals)

Typical last frost June 4 (3 days later than the 30-year normal), typical first fall frost September 22. Frost-free season 111 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 Wilbur: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 22, 20% June 14, 30% June 9, 40% June 5, 50% June 1, 60% May 28, 70% May 21, 80% May 16, 90% May 10. Observed last spring frost in recent years: 2021 June 6, 2022 May 28, 2024 June 16, 2025 May 21, 2026 June 9.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jul 1Jun 22Jun 1May 102021: June 62022: May 282024: June 162025: May 212026: June 9Fall at Wilbur: chance of a frost before this dateFall, chance of a frost before the date: 10% September 2, 20% September 7, 30% September 12, 40% September 18, 50% September 22, 60% September 25, 70% September 29, 80% October 1, 90% October 5. Observed first fall frost in recent years: 2021 August 31, 2022 September 17, 2023 September 28, 2024 September 21, 2025 October 3.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 2Sep 22Oct 52021: August 312022: September 172023: September 282024: September 212025: October 3
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
2021June 6August 31
2022May 28September 17
2023incomplete recordSeptember 28
2024June 16September 21
2025May 21October 3
2026June 9season not over yet

What these dates mean

June 22 is the cautious spring light-frost date for Wilbur, offering a 10 % chance of a frost later than this day and therefore allowing gardeners to set out tender crops with minimal risk. The median 50 % date of June 1 marks the point at which a frost is equally likely to occur later, while the hard-frost 50 % date of May 8 indicates when a 28 °F event becomes a 50-50 possibility; hard frost can be more damaging than light frost.

In the fall, September 2 serves as the cautious light-frost date, with only a 10 % chance that a frost has arrived earlier, so gardeners can plan to finish harvesting tender crops by then. The 50 % median of September 22 signals an even chance that a frost will occur earlier, and the hard-frost 50 % date of October 3 shows when a 28 °F freeze reaches a 50-50 likelihood. A hard frost at 28 °F can injure plants that would survive a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after June 22" 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 2" 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 Wilbur, WANumbered nearest stations: 1 — Coulee Dam, WA — 18 mi; 2 — Davenport, WA — 27 mi; 3 — Odessa, WA — 30 mi; 4 — near Bridgeport, WA — 46 mi; 5 — Ritzville, WA — 48 mi.WA25 mi · 40 km1. Coulee Dam, WA — 18 mi12. Davenport, WA — 27 mi23. Odessa, WA — 30 mi34. near Bridgeport, WA — 46 mi45. Ritzville, WA — 48 mi5
  1. Coulee Dam, WA 18 mi (29 km)
  2. Davenport, WA 27 mi (44 km)
  3. Odessa, WA 30 mi (48 km)
  4. near Bridgeport, WA 46 mi (73 km)
  5. Ritzville, WA 48 mi (77 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: 47.7681, -118.7239.