U.S. Frost Dates by Weather Station

NOAA station USC00457059 · Washington

Frost Dates for Ritzville, WA

NOAA weather station Ritzville 1 SSE (USC00457059), Washington · elevation 1864 ft (568 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 27only 1 spring in 10 still has a frost later
  • Typical last frostMay 750% chance of a frost after it
  • Typical first fall frostOctober 1050% chance of a frost before it
  • Frost-free season153 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Ritzville, WASpring: a frost after April 25 in 9 years out of 10, after May 7 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 10 in half of the years, before October 25 in 9 years out of 10. Typical frost-free season: 153 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 7First frost ~Oct 10Frost season at Ritzville, WASpring: a frost after April 25 in 9 years out of 10, after May 7 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 10 in half of the years, before October 25 in 9 years out of 10. Typical frost-free season: 153 days.JFMAMJJASONDLast frost ~May 7First frost ~Oct 10
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 27September 27
50% (typical)May 7October 10
90% (likely)April 25October 25
Frost-free season (32°F, 50% chance)
153 days
Hard frost (28°F), last in spring, 50% chance after
April 25
Hard frost (28°F), first in fall, 50% chance before
October 21

The last 15 years (2006–2020 normals)

Typical last frost May 8 (1 day later than the 30-year normal), typical first fall frost October 10. Frost-free season 155 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 Ritzville: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 27, 20% May 18, 30% May 13, 40% May 10, 50% May 7, 60% May 4, 70% May 1, 80% April 29, 90% April 25. Observed last spring frost in recent years: 2021 May 10, 2022 May 20, 2023 April 25, 2024 May 3, 2025 April 23, 2026 May 17.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 27May 7Apr 252021: May 102022: May 202023: April 252024: May 32025: April 232026: May 17Fall at Ritzville: chance of a frost before this dateFall, chance of a frost before the date: 10% September 27, 20% October 1, 30% October 4, 40% October 6, 50% October 10, 60% October 12, 70% October 15, 80% October 19, 90% October 25. Observed first fall frost in recent years: 2021 October 9, 2022 October 23, 2023 October 27, 2024 October 1, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 10Oct 252021: October 92022: October 232023: October 272024: October 12025: October 6
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 10October 9
2022May 20October 23
2023April 25October 27
2024May 3October 1
2025April 23October 6
2026May 17season not over yet

What these dates mean

Setting out tender crops on April 25 is a gamble in Ritzville, because there is a 90% chance that a light frost will occur later in the season. The 50% date in spring is May 7, marking the point where the odds of a frost later are even, and the 50% date in fall is October 10, where the odds of a frost earlier are even. A cautious plan would wait until the May 27 date, which carries only a 10% chance of a later frost, and would aim to finish tender crops by September 27, which has only a 10% chance that a frost has arrived earlier.

Hard frost at 28 °F matters more than light frost at 32 °F because it can injure plants that survive the milder temperature.

How to read the probabilities

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

  • Spring: "10% after May 27" 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 27" 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 Ritzville, WANumbered nearest stations: 1 — Odessa, WA — 21 mi; 2 — Lacrosse, WA — 31 mi; 3 — St. John, WA — 37 mi; 4 — Davenport, WA — 39 mi; 5 — Wilbur, WA — 48 mi.ID25 mi · 40 km1. Odessa, WA — 21 mi12. Lacrosse, WA — 31 mi23. St. John, WA — 37 mi34. Davenport, WA — 39 mi45. Wilbur, WA — 48 mi5
  1. Odessa, WA 21 mi (34 km)
  2. Lacrosse, WA 31 mi (50 km)
  3. St. John, WA 37 mi (59 km)
  4. Davenport, WA 39 mi (62 km)
  5. Wilbur, 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: 47.1175, -118.3714.