U.S. Frost Dates by Weather Station

NOAA station USC00458034 · Washington

Frost Dates for Startup, WA

NOAA weather station Startup 1 E (USC00458034), Washington · elevation 170 ft (52 m) · hardiness zone 8b*

  • Lower-risk planting dateafter May 7only 1 spring in 10 still has a frost later
  • Typical last frostApril 1550% chance of a frost after it
  • Typical first fall frostOctober 2550% chance of a frost before it
  • Frost-free season192 daystypical year, 32°F
  • Hardiness zone8bcalculated*

The year at a glance

Frost season at Startup, WASpring: a frost after March 25 in 9 years out of 10, after April 15 in half of the years, after May 7 in 1 year out of 10. Fall: the first frost comes before October 5 in 1 year out of 10, before October 25 in half of the years, before November 15 in 9 years out of 10. Typical frost-free season: 192 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 15First frost ~Oct 25Frost season at Startup, WASpring: a frost after March 25 in 9 years out of 10, after April 15 in half of the years, after May 7 in 1 year out of 10. Fall: the first frost comes before October 5 in 1 year out of 10, before October 25 in half of the years, before November 15 in 9 years out of 10. Typical frost-free season: 192 days.JFMAMJJASONDLast frost ~Apr 15First frost ~Oct 25
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 7October 5
50% (typical)April 15October 25
90% (likely)March 25November 15
Frost-free season (32°F, 50% chance)
192 days
Hard frost (28°F), last in spring, 50% chance after
March 18
Hard frost (28°F), first in fall, 50% chance before
November 12

The last 15 years (2006–2020 normals)

Typical last frost April 16 (1 day later than the 30-year normal), typical first fall frost October 21 (4 days earlier). Frost-free season 188 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 Startup: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 7, 20% May 1, 30% April 26, 40% April 20, 50% April 15, 60% April 10, 70% April 6, 80% April 1, 90% March 25. Observed last spring frost in recent years: 2021 April 14, 2022 April 20, 2023 April 14, 2024 May 8, 2025 April 16, 2026 April 10.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 7Apr 15Mar 252021: April 142022: April 202023: April 142024: May 82025: April 162026: April 10Fall at Startup: chance of a frost before this dateFall, chance of a frost before the date: 10% October 5, 20% October 13, 30% October 17, 40% October 21, 50% October 25, 60% October 28, 70% November 1, 80% November 7, 90% November 15. Observed first fall frost in recent years: 2021 October 12, 2022 November 9, 2023 October 27, 2024 November 16, 2025 October 14.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 5Oct 25Nov 152021: October 122022: November 92023: October 272024: November 162025: 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 14October 12
2022April 20November 9
2023April 14October 27
2024May 8November 16
2025April 16October 14
2026April 10season not over yet

What these dates mean

Setting out tender crops on March 25 in Startup is a gamble, because there is a 90 % chance that a light frost will occur later in the season. By contrast, planting after May 7 reduces that risk to a 10 % chance, making May 7 the cautious spring benchmark for tender crops.

The 50 % dates mark the point at which the odds of a light frost are even. In spring the median date is April 15, while in fall the median date is October 25. Those dates are not frost thresholds but simply the middle of the probability range. The hard-frost (28 °F) median dates are March 18 in spring and November 12 in fall.

For a cautious approach, tender crops should be finished by October 5 in the fall, when only a 10 % chance exists that a light frost has arrived earlier. A hard frost matters more than a light frost because the lower temperature can cause substantially greater damage to plants.

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 5" 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 Startup, WANumbered nearest stations: 1 — Everett, WA — 23 mi; 2 — near Kirkland, WA — 28 mi; 3 — near Wilderness Rim, WA — 31 mi; 4 — Palmer, WA — 39 mi; 5 — Kent, WA — 40 mi.WA25 mi · 40 km1. Everett, WA — 23 mi12. near Kirkland, WA — 28 mi23. near Wilderness Rim, WA — 31 mi34. Palmer, WA — 39 mi45. Kent, WA — 40 mi5
  1. Everett, WA 23 mi (38 km)
  2. near Kirkland, WA 28 mi (45 km)
  3. near Wilderness Rim, WA 31 mi (50 km)
  4. Palmer, WA 39 mi (63 km)
  5. Kent, WA 40 mi (64 km)

Sources

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

Station coordinates: 47.8664, -121.7175.