U.S. Frost Dates by Weather Station

NOAA station USC00451160 · Washington

Frost Dates near Carson, WA

NOAA weather station Carson Fish Hatchery (USC00451160), Washington · elevation 1134 ft (346 m) · hardiness zone 8a*

Carson is the nearest town to the station (12.3 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter May 20only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 950% chance of a frost before it
  • Frost-free season161 daystypical year, 32°F
  • Hardiness zone8acalculated*

The year at a glance

Frost season near Carson, WASpring: a frost after April 15 in 9 years out of 10, after May 2 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 9 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 161 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 9Frost season near Carson, WASpring: a frost after April 15 in 9 years out of 10, after May 2 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 9 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 161 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 9
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 20September 22
50% (typical)May 2October 9
90% (likely)April 15November 1
Frost-free season (32°F, 50% chance)
161 days
Hard frost (28°F), last in spring, 50% chance after
April 7
Hard frost (28°F), first in fall, 50% chance before
October 30

The last 15 years (2006–2020 normals)

Typical last frost April 30 (2 days earlier than the 30-year normal), typical first fall frost October 15 (6 days later). Frost-free season 166 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 near Carson: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 20, 20% May 13, 30% May 9, 40% May 5, 50% May 2, 60% April 30, 70% April 27, 80% April 23, 90% April 15. Observed last spring frost in recent years: 2021 May 20, 2022 May 19, 2023 April 30, 2024 May 2, 2025 May 4, 2026 April 28.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Jun 1May 20May 2Apr 152021: May 202022: May 192023: April 302024: May 22025: May 42026: April 28Fall near Carson: chance of a frost before this dateFall, chance of a frost before the date: 10% September 22, 20% September 28, 30% October 2, 40% October 6, 50% October 9, 60% October 13, 70% October 18, 80% October 24, 90% November 1. Observed first fall frost in recent years: 2021 October 12, 2022 November 6, 2023 October 17, 2024 October 21, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 22Oct 9Nov 12021: October 122022: November 62023: October 172024: October 212025: October 13
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 20October 12
2022May 19November 6
2023April 30October 17
2024May 2October 21
2025May 4October 13
2026April 28season not over yet

What these dates mean

The 161 days between the 32°F 50% dates in the Carson area define the span in which light frosts are less than 50 % likely, giving gardeners a window for most seasonal activities. The median dates for a 32°F event are May 2 in spring and October 9 in fall; each marks a 50 % chance that a frost will occur later (spring) or earlier (fall). The cautious spring date for setting out tender crops is May 20, when only a 10 % chance of a later frost remains, while the cautious fall date to finish harvesting tender crops is September 22, with only a 10 % chance that a frost has already arrived.

The 50% dates for a hard frost are April 7 in spring and October 30 in fall, indicating an even odds of a 28 °F event. A hard frost matters more than a light frost because temperatures at 28 °F can injure plants that survive the milder 32 °F light 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 20" 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 22" 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 Carson, WANumbered nearest stations: 1 — near Cascade Locks, OR — 16 mi; 2 — Cougar, WA — 17 mi; 3 — Battle Ground, WA — 28 mi; 4 — near Sandy, OR — 30 mi; 5 — Vancouver, WA — 35 mi.ORWA25 mi · 40 km1. near Cascade Locks, OR — 16 mi12. Cougar, WA — 17 mi23. Battle Ground, WA — 28 mi34. near Sandy, OR — 30 mi45. Vancouver, WA — 35 mi5
  1. near Cascade Locks, OR 16 mi (26 km)
  2. Cougar, WA 17 mi (28 km)
  3. Battle Ground, WA 28 mi (44 km)
  4. near Sandy, OR 30 mi (49 km)
  5. Vancouver, WA 35 mi (57 km)

Sources

* Hardiness zone 8a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 45.8678, -121.9733.