U.S. Frost Dates by Weather Station

NOAA station USW00024141 · Washington

Frost Dates for Ephrata, WA

NOAA weather station Ephrata Municipal Airport (USW00024141), Washington · elevation 1252 ft (382 m) · hardiness zone 7a*

  • Lower-risk planting dateafter May 6only 1 spring in 10 still has a frost later
  • Typical last frostApril 2250% chance of a frost after it
  • Typical first fall frostOctober 1750% chance of a frost before it
  • Frost-free season175 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Ephrata, WASpring: a frost after April 8 in 9 years out of 10, after April 22 in half of the years, after May 6 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 17 in half of the years, before October 28 in 9 years out of 10. Typical frost-free season: 175 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 22First frost ~Oct 17Frost season at Ephrata, WASpring: a frost after April 8 in 9 years out of 10, after April 22 in half of the years, after May 6 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 17 in half of the years, before October 28 in 9 years out of 10. Typical frost-free season: 175 days.JFMAMJJASONDLast frost ~Apr 22First frost ~Oct 17
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 6October 3
50% (typical)April 22October 17
90% (likely)April 8October 28
Frost-free season (32°F, 50% chance)
175 days
Hard frost (28°F), last in spring, 50% chance after
April 6
Hard frost (28°F), first in fall, 50% chance before
October 27

The last 15 years (2006–2020 normals)

Typical last frost April 22 (same as the 30-year normal), typical first fall frost October 15 (2 days earlier). Frost-free season 175 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 Ephrata: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 6, 20% May 1, 30% April 29, 40% April 25, 50% April 22, 60% April 19, 70% April 16, 80% April 13, 90% April 8. Observed last spring frost in recent years: 2021 April 25, 2022 May 13, 2023 April 20, 2024 May 2, 2025 April 17, 2026 April 26.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 6Apr 22Apr 82021: April 252022: May 132023: April 202024: May 22025: April 172026: April 26Fall at Ephrata: chance of a frost before this dateFall, chance of a frost before the date: 10% October 3, 20% October 8, 30% October 12, 40% October 15, 50% October 17, 60% October 19, 70% October 22, 80% October 24, 90% October 28. Observed first fall frost in recent years: 2021 October 9, 2022 October 25, 2023 October 27, 2024 October 18, 2025 October 16.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 3Oct 17Oct 282021: October 92022: October 252023: October 272024: October 182025: October 16
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 25October 9
2022May 13October 25
2023April 20October 27
2024May 2October 18
2025April 17October 16
2026April 26season not over yet

What these dates mean

The 175 days between the 32 °F 50% dates—April 22 and October 17—contain the period when a light frost is less likely than not, defining the core growing window for Ephrata. The 50% dates themselves mean that on April 22 there is an even chance of a frost occurring later in spring, and on October 17 there is an even chance of a frost having arrived earlier in fall.

For a cautious plan, gardeners use the May 6 spring date, which carries only a 10 % chance of a frost later, to set out tender crops, and the October 3 fall date, which carries only a 10 % chance of a frost earlier, to finish harvesting tender crops. By contrast, planting on April 8 or extending crops to October 28 involves a 90 % chance of frost and is a gamble.

The hard-frost 50% dates—April 6 and October 27—mark when a 28 °F frost is equally likely, and hard frost matters more because temperatures that low can damage plant tissue that would survive a light 32 °F frost.

How to read the probabilities

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

  • Spring: "10% after May 6" 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 3" 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 Ephrata, WANumbered nearest stations: 1 — Wenatchee (Pangborn Airport), WA — 33 mi; 2 — Wenatchee, WA — 38 mi; 3 — Odessa, WA — 38 mi; 4 — Chelan, WA — 43 mi; 5 — near Entiat, WA — 46 mi.WA25 mi · 40 km1. Wenatchee (Pangborn Airport), WA — 33 mi12. Wenatchee, WA — 38 mi23. Odessa, WA — 38 mi34. Chelan, WA — 43 mi45. near Entiat, WA — 46 mi5
  1. Wenatchee (Pangborn Airport), WA 33 mi (53 km)
  2. Wenatchee, WA 38 mi (61 km)
  3. Odessa, WA 38 mi (62 km)
  4. Chelan, WA 43 mi (69 km)
  5. near Entiat, WA 46 mi (75 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: 47.3078, -119.5153.