U.S. Frost Dates by Weather Station

NOAA station USC00104140 · Idaho

Frost Dates for Hazelton, ID

NOAA weather station Hazelton (USC00104140), Idaho · elevation 4060 ft (1238 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 750% chance of a frost after it
  • Typical first fall frostOctober 550% chance of a frost before it
  • Frost-free season149 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Hazelton, IDSpring: a frost after April 24 in 9 years out of 10, after May 7 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 5 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 149 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 7First frost ~Oct 5Frost season at Hazelton, IDSpring: a frost after April 24 in 9 years out of 10, after May 7 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 5 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 149 days.JFMAMJJASONDLast frost ~May 7First frost ~Oct 5
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.Today

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)May 26September 19
50% (typical)May 7October 5
90% (likely)April 24October 19
Frost-free season (32°F, 50% chance)
149 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost May 8 (1 day later than the 30-year normal), typical first fall frost October 6 (1 day later). Frost-free season 151 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 Hazelton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 17, 30% May 13, 40% May 10, 50% May 7, 60% May 4, 70% May 2, 80% April 29, 90% April 24.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 7Apr 24Fall at Hazelton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 19, 20% September 25, 30% September 29, 40% October 1, 50% October 5, 60% October 7, 70% October 10, 80% October 14, 90% October 19.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 19Oct 5Oct 19
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.

What these dates mean

May 26 is the cautious spring date for light frost, giving a gardener only a 10 % chance that a frost will occur later and allowing tender crops to be set out with minimal risk. In fall, September 19 is the cautious date, with a 10 % chance that a frost has already arrived, so harvesting tender crops can be finished by then.

The 50% light-frost dates are May 7 in spring and October 5 in fall; each marks the point where the chance of a frost is even. These median dates help a gardener gauge the balance of risk when timing planting or harvest. The 50% hard-frost dates are April 23 for spring and October 17 for fall. A hard frost at 28 °F can damage plant tissue that survives 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 May 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 September 19" 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 Hazelton, IDNumbered nearest stations: 1 — Paul, ID — 19 mi; 2 — Burley, ID — 19 mi; 3 — Shoshone, ID — 27 mi; 4 — Oakley, ID — 28 mi; 5 — Richfield, ID — 31 mi.UT25 mi · 40 km1. Paul, ID — 19 mi12. Burley, ID — 19 mi23. Shoshone, ID — 27 mi34. Oakley, ID — 28 mi45. Richfield, ID — 31 mi5
  1. Paul, ID 19 mi (31 km)
  2. Burley, ID 19 mi (31 km)
  3. Shoshone, ID 27 mi (44 km)
  4. Oakley, ID 28 mi (45 km)
  5. Richfield, ID 31 mi (51 km)

Sources

* Hardiness zone 6b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 42.5972, -114.1378.