U.S. Frost Dates by Weather Station

NOAA station USC00452030 · Washington

Frost Dates for Dayton, WA

NOAA weather station Dayton 1 WSW (USC00452030), Washington · elevation 1557 ft (475 m) · hardiness zone 7a*

  • Lower-risk planting dateafter May 14only 1 spring in 10 still has a frost later
  • Typical last frostApril 2850% chance of a frost after it
  • Typical first fall frostOctober 1350% chance of a frost before it
  • Frost-free season168 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Dayton, WASpring: a frost after April 11 in 9 years out of 10, after April 28 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 13 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 168 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 28First frost ~Oct 13Frost season at Dayton, WASpring: a frost after April 11 in 9 years out of 10, after April 28 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 13 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 168 days.JFMAMJJASONDLast frost ~Apr 28First frost ~Oct 13
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)May 14September 30
50% (typical)April 28October 13
90% (likely)April 11October 29
Frost-free season (32°F, 50% chance)
168 days
Hard frost (28°F), last in spring, 50% chance after
April 6
Hard frost (28°F), first in fall, 50% chance before
October 25

The last 15 years (2006–2020 normals)

Typical last frost April 28 (same as the 30-year normal), typical first fall frost October 11 (2 days earlier). Frost-free season 168 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 Dayton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 14, 20% May 8, 30% May 4, 40% April 30, 50% April 28, 60% April 25, 70% April 22, 80% April 17, 90% April 11. Observed last spring frost in recent years: 2021 April 21, 2022 May 11, 2023 April 20, 2024 April 22, 2026 April 26.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 14Apr 28Apr 112021: April 212022: May 112023: April 202024: April 222026: April 26Fall at Dayton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 30, 20% October 4, 30% October 7, 40% October 10, 50% October 13, 60% October 16, 70% October 20, 80% October 24, 90% October 29. Observed first fall frost in recent years: 2021 October 9, 2022 October 22, 2023 October 28, 2024 October 18, 2025 October 15.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 30Oct 13Oct 292021: October 92022: October 222023: October 282024: October 182025: October 15
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 21October 9
2022May 11October 22
2023April 20October 28
2024April 22October 18
2025incomplete recordOctober 15
2026April 26season not over yet

What these dates mean

The 168 days between the 50% dates in Dayton define the span when the average chance of a light frost stays below 50 percent, framing the core growing window. The 50% date is April 28 for spring, which carries a 50% chance of a frost later than this date, and the 50% date is October 13 for fall, which carries a 50% chance of a frost earlier than this date.

For a cautious approach, gardeners should wait until the May 14 spring date, which carries only a 10% chance of a later frost, before setting out tender crops, and should aim to finish tender harvests by the September 30 fall date, which also carries a 10% chance of an earlier frost. Planting on April 11 or keeping crops until October 29 would involve a 90% gamble. A hard frost, recorded at 28 °F, can cause far more severe damage than a light frost at 32 °F, so the median hard-frost dates of April 6 and October 25 are especially relevant for protecting vulnerable plants.

How to read the probabilities

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

  • Spring: "10% after May 14" 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 30" 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 Dayton, WANumbered nearest stations: 1 — Walla Walla, WA — 20 mi; 2 — Whitman Mission, WA — 29 mi; 3 — Milton Freewater, OR — 32 mi; 4 — Lacrosse, WA — 35 mi; 5 — near Burbank, WA — 42 mi.WAORID25 mi · 40 km1. Walla Walla, WA — 20 mi12. Whitman Mission, WA — 29 mi23. Milton Freewater, OR — 32 mi34. Lacrosse, WA — 35 mi45. near Burbank, WA — 42 mi5
  1. Walla Walla, WA 20 mi (33 km)
  2. Whitman Mission, WA 29 mi (47 km)
  3. Milton Freewater, OR 32 mi (52 km)
  4. Lacrosse, WA 35 mi (56 km)
  5. near Burbank, WA 42 mi (68 km)

Sources

* Hardiness zone 7a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 46.3153, -118.0022.