U.S. Frost Dates by Weather Station

NOAA station USC00356634 · Oregon

Frost Dates for Pilot Rock, OR

NOAA weather station Pilot Rock 1 SE (USC00356634), Oregon · elevation 1720 ft (524 m) · hardiness zone 7a*

  • Lower-risk planting dateafter May 28only 1 spring in 10 still has a frost later
  • Typical last frostMay 750% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season147 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Pilot Rock, ORSpring: a frost after April 24 in 9 years out of 10, after May 7 in half of the years, after May 28 in 1 year out of 10. Fall: the first frost comes before September 16 in 1 year out of 10, before October 4 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 147 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 7First frost ~Oct 4Frost season at Pilot Rock, ORSpring: a frost after April 24 in 9 years out of 10, after May 7 in half of the years, after May 28 in 1 year out of 10. Fall: the first frost comes before September 16 in 1 year out of 10, before October 4 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 147 days.JFMAMJJASONDLast frost ~May 7First frost ~Oct 4
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 28September 16
50% (typical)May 7October 4
90% (likely)April 24October 17
Frost-free season (32°F, 50% chance)
147 days
Hard frost (28°F), last in spring, 50% chance after
April 21
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 9 (2 days later than the 30-year normal), typical first fall frost October 4. Frost-free season 148 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 Pilot Rock: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 28, 20% May 19, 30% May 15, 40% May 11, 50% May 7, 60% May 4, 70% May 2, 80% April 30, 90% April 24. Observed last spring frost in recent years: 2022 May 13.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 28May 7Apr 242022: May 13Fall at Pilot Rock: chance of a frost before this dateFall, chance of a frost before the date: 10% September 16, 20% September 24, 30% September 28, 40% October 1, 50% October 4, 60% October 6, 70% October 9, 80% October 12, 90% October 17.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 16Oct 4Oct 17
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
2021incomplete recordincomplete record
2022May 13incomplete record
2023no datano data
2024no datano data
2025no datano data
2026no dataseason not over yet

What these dates mean

The 147 days between the 50% light-frost dates in Pilot Rock define the core growing window for tender crops. May 7 is the 50% date for light frost in spring, meaning a 50% chance of a frost later than this date, and October 4 is the 50% date for light frost in fall, meaning a 50% chance of a frost earlier than this date.

Gardeners who prefer a cautious plan would wait until the cautious spring date of May 28, which carries only a 10% chance of a later frost, before setting out tender crops, and aim to finish harvesting tender crops by the cautious fall date of September 16, when there is only a 10% chance that a frost has already arrived. Hard frost at 28 °F, marked by the dates April 21 and October 15, is a more severe threat to plants than the 32 °F light-frost threshold.

How to read the probabilities

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

  • Spring: "10% after May 28" 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 16" 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 Pilot Rock, ORNumbered nearest stations: 1 — Pendleton, OR — 15 mi; 2 — Heppner, OR — 37 mi; 3 — Milton Freewater, OR — 38 mi; 4 — La Grande, OR — 38 mi; 5 — Whitman Mission, WA — 43 mi.WA25 mi · 40 km1. Pendleton, OR — 15 mi12. Heppner, OR — 37 mi23. Milton Freewater, OR — 38 mi34. La Grande, OR — 38 mi45. Whitman Mission, WA — 43 mi5
  1. Pendleton, OR 15 mi (24 km)
  2. Heppner, OR 37 mi (59 km)
  3. Milton Freewater, OR 38 mi (61 km)
  4. La Grande, OR 38 mi (61 km)
  5. Whitman Mission, WA 43 mi (69 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: 45.4756, -118.8253.