U.S. Frost Dates by Weather Station

NOAA station USC00108928 · Idaho

Frost Dates near Murphy, ID

NOAA weather station Swan Falls Powerhouse (USC00108928), Idaho · elevation 2325 ft (709 m) · hardiness zone 7b*

Murphy is the nearest town to the station (8.9 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 May 6only 1 spring in 10 still has a frost later
  • Typical last frostApril 1250% chance of a frost after it
  • Typical first fall frostOctober 2650% chance of a frost before it
  • Frost-free season193 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season near Murphy, IDSpring: a frost after March 23 in 9 years out of 10, after April 12 in half of the years, after May 6 in 1 year out of 10. Fall: the first frost comes before October 9 in 1 year out of 10, before October 26 in half of the years, before November 9 in 9 years out of 10. Typical frost-free season: 193 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 12First frost ~Oct 26Frost season near Murphy, IDSpring: a frost after March 23 in 9 years out of 10, after April 12 in half of the years, after May 6 in 1 year out of 10. Fall: the first frost comes before October 9 in 1 year out of 10, before October 26 in half of the years, before November 9 in 9 years out of 10. Typical frost-free season: 193 days.JFMAMJJASONDLast frost ~Apr 12First 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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 6October 9
50% (typical)April 12October 26
90% (likely)March 23November 9
Frost-free season (32°F, 50% chance)
193 days
Hard frost (28°F), last in spring, 50% chance after
March 23
Hard frost (28°F), first in fall, 50% chance before
November 5

The last 15 years (2006–2020 normals)

Typical last frost April 7 (5 days earlier than the 30-year normal), typical first fall frost October 30 (4 days later). Frost-free season 205 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 Murphy: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 6, 20% April 28, 30% April 22, 40% April 17, 50% April 12, 60% April 8, 70% April 4, 80% March 31, 90% March 23. Observed last spring frost in recent years: 2021 April 11, 2022 May 10, 2023 April 20, 2024 March 16, 2025 March 19, 2026 April 17.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 6Apr 12Mar 232021: April 112022: May 102023: April 202024: March 162025: March 192026: April 17Fall near Murphy: chance of a frost before this dateFall, chance of a frost before the date: 10% October 9, 20% October 17, 30% October 21, 40% October 24, 50% October 26, 60% October 29, 70% October 31, 80% November 4, 90% November 9. Observed first fall frost in recent years: 2021 November 8, 2022 October 27, 2023 October 28, 2024 October 25, 2025 October 28.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 9Oct 26Nov 92021: November 82022: October 272023: October 282024: October 252025: October 28
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 11November 8
2022May 10October 27
2023April 20October 28
2024March 16October 25
2025March 19October 28
2026April 17season not over yet

What these dates mean

Setting out tender crops on March 23 is a gamble for gardeners in the Murphy area, because there is a 90% chance of a light frost later. The cautious spring date for gardeners is May 6, which carries only a 10% chance of a light frost later.

In the fall, the cautious date for gardeners is October 9, with a 10% chance of a light frost earlier. The 50% light-frost dates are April 12 and October 26; April 12 holds a 50% chance of a light frost later, while October 26 holds a 50% chance of a light frost earlier. The 50% hard-frost dates are March 23 in spring and November 5 in fall.

A hard frost at 28 °F can damage plants that survive a light frost at 32 °F, so it is a more critical 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 6" 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 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 Murphy, IDNumbered nearest stations: 1 — Boise (Air Terminal), ID — 23 mi; 2 — near Hidden Spring, ID — 35 mi; 3 — Emmett, ID — 42 mi; 4 — Garden Valley, ID — 63 mi; 5 — Payette, ID — 64 mi.IDOR25 mi · 40 km1. Boise (Air Terminal), ID — 23 mi12. near Hidden Spring, ID — 35 mi23. Emmett, ID — 42 mi34. Garden Valley, ID — 63 mi45. Payette, ID — 64 mi5
  1. Boise (Air Terminal), ID 23 mi (38 km)
  2. near Hidden Spring, ID 35 mi (57 km)
  3. Emmett, ID 42 mi (68 km)
  4. Garden Valley, ID 63 mi (101 km)
  5. Payette, ID 64 mi (103 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: 43.2436, -116.3783.