U.S. Frost Dates by Weather Station

NOAA station USC00451767 · Washington

Frost Dates for Coulee Dam, WA

NOAA weather station Coulee Dam 1 SW (USC00451767), Washington · elevation 1719 ft (524 m) · hardiness zone 7a*

  • Lower-risk planting dateafter May 7only 1 spring in 10 still has a frost later
  • Typical last frostApril 2250% chance of a frost after it
  • Typical first fall frostOctober 2150% chance of a frost before it
  • Frost-free season180 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Coulee Dam, WASpring: a frost after April 5 in 9 years out of 10, after April 22 in half of the years, after May 7 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 21 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 180 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 22First frost ~Oct 21Frost season at Coulee Dam, WASpring: a frost after April 5 in 9 years out of 10, after April 22 in half of the years, after May 7 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 21 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 180 days.JFMAMJJASONDLast frost ~Apr 22First frost ~Oct 21
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 7October 6
50% (typical)April 22October 21
90% (likely)April 5November 5
Frost-free season (32°F, 50% chance)
180 days
Hard frost (28°F), last in spring, 50% chance after
April 1
Hard frost (28°F), first in fall, 50% chance before
November 1

The last 15 years (2006–2020 normals)

Typical last frost April 23 (1 day later than the 30-year normal), typical first fall frost October 21. Frost-free season 181 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 Coulee Dam: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 7, 20% May 2, 30% April 29, 40% April 25, 50% April 22, 60% April 19, 70% April 15, 80% April 11, 90% April 5. Observed last spring frost in recent years: 2021 April 12, 2022 May 8, 2023 April 20, 2024 April 30, 2025 April 17, 2026 April 27.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 7Apr 22Apr 52021: April 122022: May 82023: April 202024: April 302025: April 172026: April 27Fall at Coulee Dam: chance of a frost before this dateFall, chance of a frost before the date: 10% October 6, 20% October 12, 30% October 16, 40% October 18, 50% October 21, 60% October 24, 70% October 27, 80% October 31, 90% November 5. Observed first fall frost in recent years: 2021 October 11, 2022 November 3, 2023 October 25, 2024 October 23, 2025 October 14.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 6Oct 21Nov 52021: October 112022: November 32023: October 252024: October 232025: October 14
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 12October 11
2022May 8November 3
2023April 20October 25
2024April 30October 23
2025April 17October 14
2026April 27season not over yet

What these dates mean

Between the two 32°F 50% dates—April 22 and October 21—there are 180 days in which tender crops can be grown in Coulee Dam. The 50% dates mark the point where a light frost is equally likely to occur later (in spring) or earlier (in fall), giving a neutral reference for planning.

The cautious spring date for setting out tender crops is May 7, when only a 10 % chance of a light frost remains; planting on April 5 carries a 90 % chance and is a gamble. In the fall the cautious date to finish harvesting tender crops is October 6, with a 10 % chance of a light frost already having arrived; waiting until November 5 entails a 90 % chance and is risky.

A hard frost, defined at 28°F, is more damaging than a light frost at 32°F, so the 50% hard-frost dates of April 1 in spring and November 1 in fall are important reference points for gardeners.

How to read the probabilities

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

  • Spring: "10% after May 7" 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 6" 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 Coulee Dam, WANumbered nearest stations: 1 — Wilbur, WA — 18 mi; 2 — near Bridgeport, WA — 30 mi; 3 — Davenport, WA — 44 mi; 4 — Odessa, WA — 45 mi; 5 — Chelan, WA — 47 mi.WA25 mi · 40 km1. Wilbur, WA — 18 mi12. near Bridgeport, WA — 30 mi23. Davenport, WA — 44 mi34. Odessa, WA — 45 mi45. Chelan, WA — 47 mi5
  1. Wilbur, WA 18 mi (29 km)
  2. near Bridgeport, WA 30 mi (49 km)
  3. Davenport, WA 44 mi (71 km)
  4. Odessa, WA 45 mi (73 km)
  5. Chelan, WA 47 mi (76 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: 47.9544, -118.9997.