U.S. Frost Dates by Weather Station

NOAA station USW00024149 · Idaho

Frost Dates near Lewiston, ID

NOAA weather station Lewiston Nez Perce County Airport (USW00024149), Idaho · elevation 1436 ft (438 m) · hardiness zone 7b*

Lewiston is the nearest town to the station (2.9 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 April 26only 1 spring in 10 still has a frost later
  • Typical last frostApril 650% chance of a frost after it
  • Typical first fall frostOctober 2650% chance of a frost before it
  • Frost-free season200 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season near Lewiston, IDSpring: a frost after March 20 in 9 years out of 10, after April 6 in half of the years, after April 26 in 1 year out of 10. Fall: the first frost comes before October 10 in 1 year out of 10, before October 26 in half of the years, before November 12 in 9 years out of 10. Typical frost-free season: 200 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 6First frost ~Oct 26Frost season near Lewiston, IDSpring: a frost after March 20 in 9 years out of 10, after April 6 in half of the years, after April 26 in 1 year out of 10. Fall: the first frost comes before October 10 in 1 year out of 10, before October 26 in half of the years, before November 12 in 9 years out of 10. Typical frost-free season: 200 days.JFMAMJJASONDLast frost ~Apr 6First frost ~Oct 26
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)April 26October 10
50% (typical)April 6October 26
90% (likely)March 20November 12
Frost-free season (32°F, 50% chance)
200 days
Hard frost (28°F), last in spring, 50% chance after
March 15
Hard frost (28°F), first in fall, 50% chance before
November 8

The last 15 years (2006–2020 normals)

Typical last frost April 11 (5 days later than the 30-year normal), typical first fall frost October 25 (1 day earlier). Frost-free season 198 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 Lewiston: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 26, 20% April 19, 30% April 14, 40% April 10, 50% April 6, 60% April 3, 70% March 31, 80% March 27, 90% March 20. Observed last spring frost in recent years: 2021 April 12, 2022 April 17, 2023 April 20, 2024 March 25, 2025 April 1, 2026 April 25.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 26Apr 6Mar 202021: April 122022: April 172023: April 202024: March 252025: April 12026: April 25Fall near Lewiston: chance of a frost before this dateFall, chance of a frost before the date: 10% October 10, 20% October 14, 30% October 18, 40% October 23, 50% October 26, 60% October 29, 70% November 1, 80% November 5, 90% November 12. Observed first fall frost in recent years: 2021 October 12, 2022 November 7, 2023 October 27, 2024 November 6, 2025 November 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Dec 1Oct 10Oct 26Nov 122021: October 122022: November 72023: October 272024: November 62025: November 24
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 12October 12
2022April 17November 7
2023April 20October 27
2024March 25November 6
2025April 1November 24
2026April 25season not over yet

What these dates mean

October 10 is the cautious fall date in the Lewiston area for finishing the harvest of tender crops, because there is only a ten percent chance that a light frost has arrived earlier. The median point for light frost in fall is October 26, a fifty percent chance of a frost earlier than that date, while the hard-frost median is November 8.

The fifty percent dates for light frost are April 6 in spring and October 26 in fall; each marks the point where the chance of a frost later (spring) or earlier (fall) is even. For a low-risk plan, gardeners use April 26 as the cautious spring date to set out tender crops, and October 10 as the cautious fall date to finish harvest.

Hard frosts at 28 °F are more damaging than light frosts at 32 °F because they can kill tissue that survives a light freeze, and the median hard-frost dates are March 15 in spring and November 8 in fall.

How to read the probabilities

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

  • Spring: "10% after April 26" 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 10" 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 Lewiston, IDNumbered nearest stations: 1 — Pullman, WA — 28 mi; 2 — near Orofino, ID — 34 mi; 3 — Cottonwood, ID — 38 mi; 4 — Nezperce, ID — 38 mi; 5 — Dayton, WA — 47 mi.WAID25 mi · 40 km1. Pullman, WA — 28 mi12. near Orofino, ID — 34 mi23. Cottonwood, ID — 38 mi34. Nezperce, ID — 38 mi45. Dayton, WA — 47 mi5
  1. Pullman, WA 28 mi (45 km)
  2. near Orofino, ID 34 mi (55 km)
  3. Cottonwood, ID 38 mi (61 km)
  4. Nezperce, ID 38 mi (61 km)
  5. Dayton, WA 47 mi (76 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: 46.3747, -117.0156.