U.S. Frost Dates by Weather Station

NOAA station USC00451395 · Washington

Frost Dates for Chewelah, WA

NOAA weather station Chewelah (USC00451395), Washington · elevation 1670 ft (509 m) · hardiness zone 6a*

  • Lower-risk planting dateafter June 7only 1 spring in 10 still has a frost later
  • Typical last frostMay 1650% chance of a frost after it
  • Typical first fall frostSeptember 1550% chance of a frost before it
  • Frost-free season120 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Chewelah, WASpring: a frost after April 30 in 9 years out of 10, after May 16 in half of the years, after June 7 in 1 year out of 10. Fall: the first frost comes before September 1 in 1 year out of 10, before September 15 in half of the years, before September 29 in 9 years out of 10. Typical frost-free season: 120 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 16First frost ~Sep 15Frost season at Chewelah, WASpring: a frost after April 30 in 9 years out of 10, after May 16 in half of the years, after June 7 in 1 year out of 10. Fall: the first frost comes before September 1 in 1 year out of 10, before September 15 in half of the years, before September 29 in 9 years out of 10. Typical frost-free season: 120 days.JFMAMJJASONDLast frost ~May 16First frost ~Sep 15
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)June 7September 1
50% (typical)May 16September 15
90% (likely)April 30September 29
Frost-free season (32°F, 50% chance)
120 days
Hard frost (28°F), last in spring, 50% chance after
April 30
Hard frost (28°F), first in fall, 50% chance before
September 28

The last 15 years (2006–2020 normals)

Typical last frost May 14 (2 days earlier than the 30-year normal), typical first fall frost September 14 (1 day earlier). Frost-free season 123 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 Chewelah: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 7, 20% May 31, 30% May 25, 40% May 20, 50% May 16, 60% May 12, 70% May 9, 80% May 5, 90% April 30. Observed last spring frost in recent years: 2021 May 19, 2022 May 22, 2024 June 16.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 7May 16Apr 302021: May 192022: May 222024: June 16Fall at Chewelah: chance of a frost before this dateFall, chance of a frost before the date: 10% September 1, 20% September 5, 30% September 8, 40% September 12, 50% September 15, 60% September 18, 70% September 21, 80% September 24, 90% September 29. Observed first fall frost in recent years: 2021 September 21, 2022 October 9, 2023 October 1, 2024 September 21.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 1Sep 15Sep 292021: September 212022: October 92023: October 12024: September 21
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 19September 21
2022May 22October 9
2023incomplete recordOctober 1
2024June 16September 21
2025incomplete recordno data
2026no dataseason not over yet

What these dates mean

The 120 days between the 50% dates in Chewelah—May 16 and September 15—frame the period when tender crops can be grown with balanced frost risk. The 50% dates are the mid-point of the light-frost probability curve, meaning a light frost is equally likely to occur before or after each date.

For a cautious approach, spring planting should wait until the June 7 date, which carries a 10 % chance of a light frost later, while fall harvesting should aim to finish by the September 1 date, which holds a 10 % chance of a light frost earlier. Planting on April 30 or keeping crops out until September 29 involves a 90 % chance of a light frost at the opposite end of the season.

Hard frost at 28 °F is more damaging than a light frost at 32 °F; the 50% hard-frost dates are April 30 in spring and September 28 in fall.

How to read the probabilities

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

  • Spring: "10% after June 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 September 1" 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 Chewelah, WANumbered nearest stations: 1 — Priest River, ID — 42 mi; 2 — Northport, WA — 43 mi; 3 — Spokane, WA — 46 mi; 4 — Davenport, WA — 47 mi; 5 — Republic, WA — 52 mi.WAIDMT25 mi · 40 km1. Priest River, ID — 42 mi12. Northport, WA — 43 mi23. Spokane, WA — 46 mi34. Davenport, WA — 47 mi45. Republic, WA — 52 mi5
  1. Priest River, ID 42 mi (68 km)
  2. Northport, WA 43 mi (70 km)
  3. Spokane, WA 46 mi (74 km)
  4. Davenport, WA 47 mi (75 km)
  5. Republic, WA 52 mi (84 km)

Sources

* Hardiness zone 6a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 48.2733, -117.7408.