U.S. Frost Dates by Weather Station

NOAA station USC00353827 · Oregon

Frost Dates for Heppner, OR

NOAA weather station Heppner (USC00353827), Oregon · elevation 1885 ft (575 m) · hardiness zone 7a*

  • Lower-risk planting dateafter May 11only 1 spring in 10 still has a frost later
  • Typical last frostApril 2650% chance of a frost after it
  • Typical first fall frostOctober 1950% chance of a frost before it
  • Frost-free season174 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Heppner, ORSpring: a frost after April 6 in 9 years out of 10, after April 26 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 19 in half of the years, before November 2 in 9 years out of 10. Typical frost-free season: 174 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 26First frost ~Oct 19Frost season at Heppner, ORSpring: a frost after April 6 in 9 years out of 10, after April 26 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 19 in half of the years, before November 2 in 9 years out of 10. Typical frost-free season: 174 days.JFMAMJJASONDLast frost ~Apr 26First frost ~Oct 19
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 11October 3
50% (typical)April 26October 19
90% (likely)April 6November 2
Frost-free season (32°F, 50% chance)
174 days
Hard frost (28°F), last in spring, 50% chance after
April 2
Hard frost (28°F), first in fall, 50% chance before
November 1

The last 15 years (2006–2020 normals)

Typical last frost April 28 (2 days later than the 30-year normal), typical first fall frost October 17 (2 days earlier). Frost-free season 173 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 Heppner: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 11, 20% May 5, 30% May 1, 40% April 29, 50% April 26, 60% April 23, 70% April 18, 80% April 14, 90% April 6. Observed last spring frost in recent years: 2021 May 29, 2022 May 13, 2023 April 20, 2024 May 2, 2025 April 23, 2026 April 26.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Jun 1May 11Apr 26Apr 62021: May 292022: May 132023: April 202024: May 22025: April 232026: April 26Fall at Heppner: chance of a frost before this dateFall, chance of a frost before the date: 10% October 3, 20% October 8, 30% October 12, 40% October 15, 50% October 19, 60% October 22, 70% October 26, 80% October 29, 90% November 2. Observed first fall frost in recent years: 2021 October 11, 2022 November 2, 2023 October 28, 2024 October 25.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 3Oct 19Nov 22021: October 112022: November 22023: October 282024: October 25
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 29October 11
2022May 13November 2
2023April 20October 28
2024May 2October 25
2025April 23incomplete record
2026April 26season not over yet

What these dates mean

October 3 is the cautious fall date for finishing the harvest in Heppner, carrying only a 10 % chance that a light frost has arrived earlier. In spring the cautious date for setting out tender crops is May 11, when a light frost later than that day occurs with a 10 % probability; planting on April 6 would be a gamble with a 90 % chance of frost later. The 50 % dates are April 26 and October 19; there is an even odds, a 50 % chance of a light frost later than April 26 in spring and earlier than October 19 in fall.

Hard frost, defined at 28 °F, is more damaging than a light frost at 32 °F because it can injure plants that survive the milder temperature. The median hard-frost dates are April 2 and November 1, each marking the point where a hard frost has a 50 % chance of occurring.

How to read the probabilities

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

  • Spring: "10% after May 11" 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 3" 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 Heppner, ORNumbered nearest stations: 1 — Boardman, OR — 34 mi; 2 — Pilot Rock, OR — 37 mi; 3 — Pendleton, OR — 41 mi; 4 — Moro, OR — 57 mi; 5 — Kennewick, WA — 63 mi.ORWA25 mi · 40 km1. Boardman, OR — 34 mi12. Pilot Rock, OR — 37 mi23. Pendleton, OR — 41 mi34. Moro, OR — 57 mi45. Kennewick, WA — 63 mi5
  1. Boardman, OR 34 mi (55 km)
  2. Pilot Rock, OR 37 mi (59 km)
  3. Pendleton, OR 41 mi (66 km)
  4. Moro, OR 57 mi (91 km)
  5. Kennewick, WA 63 mi (101 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: 45.3653, -119.5639.