U.S. Frost Dates by Weather Station

NOAA station USC00353604 · Oregon

Frost Dates for Halfway, OR

NOAA weather station Halfway (USC00353604), Oregon · elevation 2653 ft (809 m) · hardiness zone 6a*

  • Lower-risk planting dateafter June 2only 1 spring in 10 still has a frost later
  • Typical last frostMay 1550% chance of a frost after it
  • Typical first fall frostSeptember 2450% chance of a frost before it
  • Frost-free season130 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Halfway, ORSpring: a frost after May 2 in 9 years out of 10, after May 15 in half of the years, after June 2 in 1 year out of 10. Fall: the first frost comes before September 9 in 1 year out of 10, before September 24 in half of the years, before October 6 in 9 years out of 10. Typical frost-free season: 130 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 15First frost ~Sep 24Frost season at Halfway, ORSpring: a frost after May 2 in 9 years out of 10, after May 15 in half of the years, after June 2 in 1 year out of 10. Fall: the first frost comes before September 9 in 1 year out of 10, before September 24 in half of the years, before October 6 in 9 years out of 10. Typical frost-free season: 130 days.JFMAMJJASONDLast frost ~May 15First frost ~Sep 24
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 2September 9
50% (typical)May 15September 24
90% (likely)May 2October 6
Frost-free season (32°F, 50% chance)
130 days
Hard frost (28°F), last in spring, 50% chance after
May 2
Hard frost (28°F), first in fall, 50% chance before
October 5

The last 15 years (2006–2020 normals)

Typical last frost May 14 (1 day earlier than the 30-year normal), typical first fall frost September 29 (5 days later). Frost-free season 134 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 Halfway: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 2, 20% May 28, 30% May 22, 40% May 18, 50% May 15, 60% May 13, 70% May 10, 80% May 7, 90% May 2. Observed last spring frost in recent years: 2021 May 11, 2022 May 20, 2023 May 10, 2024 May 21, 2025 May 19, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 2May 15May 22021: May 112022: May 202023: May 102024: May 212025: May 192026: May 19Fall at Halfway: chance of a frost before this dateFall, chance of a frost before the date: 10% September 9, 20% September 14, 30% September 18, 40% September 21, 50% September 24, 60% September 27, 70% September 30, 80% October 2, 90% October 6. Observed first fall frost in recent years: 2021 September 17, 2022 October 17, 2023 October 13, 2024 September 30, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 9Sep 24Oct 62021: September 172022: October 172023: October 132024: September 302025: October 6
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 11September 17
2022May 20October 17
2023May 10October 13
2024May 21September 30
2025May 19October 6
2026May 19season not over yet

What these dates mean

June 2 is the cautious spring date for Halfway, giving a gardener a 10 % chance that a light frost will occur later, so tender crops can be set out after that day with minimal risk. The 50% date of May 15 indicates a 50% chance of a light frost later than this date, while the 50% hard-frost date of May 2 marks the point where temperatures have an even chance of reaching 28 °F. In the fall, September 9 serves as the cautious date, carrying only a 10 % chance that a light frost has already arrived, making it the latest reliable day to finish harvesting tender crops. The 50% date of September 24 indicates a 50% chance of a light frost earlier than this date, and the 50% hard-frost date of October 5 shows the median point for 28 °F conditions. A hard frost is more damaging because it reaches the lower 28 °F threshold that can kill plant tissue, unlike a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after June 2" 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 9" 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 Halfway, ORNumbered nearest stations: 1 — Cambridge, ID — 30 mi; 2 — Baker City, OR — 34 mi; 3 — McCall, ID — 49 mi; 4 — Payette, ID — 56 mi; 5 — La Grande, OR — 56 mi.ID25 mi · 40 km1. Cambridge, ID — 30 mi12. Baker City, OR — 34 mi23. McCall, ID — 49 mi34. Payette, ID — 56 mi45. La Grande, OR — 56 mi5
  1. Cambridge, ID 30 mi (48 km)
  2. Baker City, OR 34 mi (55 km)
  3. McCall, ID 49 mi (79 km)
  4. Payette, ID 56 mi (90 km)
  5. La Grande, OR 56 mi (90 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: 44.8772, -117.1094.