U.S. Frost Dates by Weather Station

NOAA station USC00102942 · Idaho

Frost Dates for Emmett, ID

NOAA weather station Emmett 2 E (USC00102942), Idaho · elevation 2390 ft (729 m) · hardiness zone 7a*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostApril 3050% chance of a frost after it
  • Typical first fall frostOctober 1750% chance of a frost before it
  • Frost-free season168 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Emmett, IDSpring: a frost after April 17 in 9 years out of 10, after April 30 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before October 2 in 1 year out of 10, before October 17 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 168 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 30First frost ~Oct 17Frost season at Emmett, IDSpring: a frost after April 17 in 9 years out of 10, after April 30 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before October 2 in 1 year out of 10, before October 17 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 168 days.JFMAMJJASONDLast frost ~Apr 30First frost ~Oct 17
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 17October 2
50% (typical)April 30October 17
90% (likely)April 17November 1
Frost-free season (32°F, 50% chance)
168 days
Hard frost (28°F), last in spring, 50% chance after
April 14
Hard frost (28°F), first in fall, 50% chance before
October 28

The last 15 years (2006–2020 normals)

Typical last frost May 1 (1 day later than the 30-year normal), typical first fall frost October 19 (2 days later). Frost-free season 169 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 Emmett: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 11, 30% May 7, 40% May 3, 50% April 30, 60% April 29, 70% April 26, 80% April 22, 90% April 17. Observed last spring frost in recent years: 2022 May 11, 2023 April 21, 2024 May 1, 2025 April 23, 2026 April 28.Spring: last frostChance of a frost after this date10%50%90%May 1May 17Apr 30Apr 172022: May 112023: April 212024: May 12025: April 232026: April 28Fall at Emmett: chance of a frost before this dateFall, chance of a frost before the date: 10% October 2, 20% October 7, 30% October 11, 40% October 14, 50% October 17, 60% October 19, 70% October 22, 80% October 25, 90% November 1. Observed first fall frost in recent years: 2021 October 14, 2022 October 23, 2023 October 26, 2024 October 19, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 2Oct 17Nov 12021: October 142022: October 232023: October 262024: October 192025: October 22
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 recordOctober 14
2022May 11October 23
2023April 21October 26
2024May 1October 19
2025April 23October 22
2026April 28season not over yet

What these dates mean

The 168 days between the 32°F 50% dates in Emmett – April 30 in spring and October 17 in fall – mark the central period of the growing season, each representing an even chance of a light frost. The probabilities are drawn from 30 years of NOAA records, providing a long-term view of frost risk for this elevation. The cautious spring date is May 17, when there is only a 10 % chance of a later frost, and the cautious fall date is October 2, when only a 10 % chance of an earlier frost has occurred. The median hard-frost dates are April 14 and October 28, each indicating a 50 % chance of reaching 28 °F. Hard frost, defined by a 28°F temperature, can injure plants that survive a 32°F light frost, so it poses a greater risk.

How to read the probabilities

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

  • Spring: "10% after May 17" 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 2" 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 Emmett, IDNumbered nearest stations: 1 — near Hidden Spring, ID — 15 mi; 2 — Boise (Air Terminal), ID — 23 mi; 3 — Payette, ID — 28 mi; 4 — Garden Valley, ID — 30 mi; 5 — near Murphy, ID — 42 mi.IDOR25 mi · 40 km1. near Hidden Spring, ID — 15 mi12. Boise (Air Terminal), ID — 23 mi23. Payette, ID — 28 mi34. Garden Valley, ID — 30 mi45. near Murphy, ID — 42 mi5
  1. near Hidden Spring, ID 15 mi (25 km)
  2. Boise (Air Terminal), ID 23 mi (37 km)
  3. Payette, ID 28 mi (45 km)
  4. Garden Valley, ID 30 mi (48 km)
  5. near Murphy, ID 42 mi (68 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: 43.8544, -116.4664.