U.S. Frost Dates by Weather Station

NOAA station USC00102845 · Idaho

Frost Dates near Orofino, ID

NOAA weather station Dworshak Fish Hatchery (USC00102845), Idaho · elevation 995 ft (303 m) · hardiness zone 7b*

Orofino is the nearest town to the station (3.5 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 5only 1 spring in 10 still has a frost later
  • Typical last frostApril 2050% chance of a frost after it
  • Typical first fall frostOctober 2050% chance of a frost before it
  • Frost-free season182 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season near Orofino, IDSpring: a frost after April 1 in 9 years out of 10, after April 20 in half of the years, after May 5 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 20 in half of the years, before November 7 in 9 years out of 10. Typical frost-free season: 182 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 20First frost ~Oct 20Frost season near Orofino, IDSpring: a frost after April 1 in 9 years out of 10, after April 20 in half of the years, after May 5 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 20 in half of the years, before November 7 in 9 years out of 10. Typical frost-free season: 182 days.JFMAMJJASONDLast frost ~Apr 20First frost ~Oct 20
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 5September 30
50% (typical)April 20October 20
90% (likely)April 1November 7
Frost-free season (32°F, 50% chance)
182 days
Hard frost (28°F), last in spring, 50% chance after
March 28
Hard frost (28°F), first in fall, 50% chance before
November 2

The last 15 years (2006–2020 normals)

Typical last frost April 19 (1 day earlier than the 30-year normal), typical first fall frost October 17 (3 days earlier). Frost-free season 184 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 Orofino: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 5, 20% May 1, 30% April 27, 40% April 24, 50% April 20, 60% April 16, 70% April 12, 80% April 8, 90% April 1. Observed last spring frost in recent years: 2023 April 20, 2024 April 18, 2025 April 17, 2026 April 1.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 5Apr 20Apr 12023: April 202024: April 182025: April 172026: April 1Fall near Orofino: chance of a frost before this dateFall, chance of a frost before the date: 10% September 30, 20% October 7, 30% October 12, 40% October 17, 50% October 20, 60% October 24, 70% October 28, 80% November 1, 90% November 7. Observed first fall frost in recent years: 2022 November 2, 2023 October 27, 2024 November 5.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 30Oct 20Nov 72022: November 22023: October 272024: November 5
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
2022incomplete recordNovember 2
2023April 20October 27
2024April 18November 5
2025April 17incomplete record
2026April 1season not over yet

What these dates mean

May 5 is the cautious spring light-frost date, with only a 10 % chance of a frost later and marking the practical day a gardener can set out tender crops.

April 20 is the 50 % spring light-frost date, indicating a 50 % chance of a frost later than this date, while September 30 is the cautious fall light-frost date, carrying a 10 % chance that a frost has arrived earlier and allowing a gardener to finish harvesting tender crops. October 20 is the 50 % fall light-frost date, meaning a 50 % chance of a frost earlier than this date.

The 50 % hard-frost dates are March 28 for spring and November 2 for fall; a hard frost at 28 °F can damage plants that survive a light frost at 32 °F, making it a more critical threshold for garden planning.

How to read the probabilities

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

  • Spring: "10% after May 5" 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 30" 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 Orofino, IDNumbered nearest stations: 1 — Nezperce, ID — 19 mi; 2 — Cottonwood, ID — 33 mi; 3 — near Lewiston, ID — 34 mi; 4 — Pullman, WA — 45 mi; 5 — Saint Maries, ID — 58 mi.IDWAMT25 mi · 40 km1. Nezperce, ID — 19 mi12. Cottonwood, ID — 33 mi23. near Lewiston, ID — 34 mi34. Pullman, WA — 45 mi45. Saint Maries, ID — 58 mi5
  1. Nezperce, ID 19 mi (31 km)
  2. Cottonwood, ID 33 mi (52 km)
  3. near Lewiston, ID 34 mi (55 km)
  4. Pullman, WA 45 mi (72 km)
  5. Saint Maries, ID 58 mi (93 km)

Sources

* Hardiness zone 7b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 46.5022, -116.3217.