U.S. Frost Dates by Weather Station

NOAA station USC00426708 · Utah

Frost Dates for Partoun, UT

NOAA weather station Partoun (USC00426708), Utah · elevation 4780 ft (1457 m) · hardiness zone 6a*

  • Lower-risk planting dateafter June 5only 1 spring in 10 still has a frost later
  • Typical last frostMay 1350% chance of a frost after it
  • Typical first fall frostSeptember 2950% chance of a frost before it
  • Frost-free season137 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Partoun, UTSpring: a frost after April 28 in 9 years out of 10, after May 13 in half of the years, after June 5 in 1 year out of 10. Fall: the first frost comes before September 16 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 137 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 13First frost ~Sep 29Frost season at Partoun, UTSpring: a frost after April 28 in 9 years out of 10, after May 13 in half of the years, after June 5 in 1 year out of 10. Fall: the first frost comes before September 16 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 137 days.JFMAMJJASONDLast frost ~May 13First frost ~Sep 29
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)June 5September 16
50% (typical)May 13September 29
90% (likely)April 28October 11
Frost-free season (32°F, 50% chance)
137 days
Hard frost (28°F), last in spring, 50% chance after
April 30
Hard frost (28°F), first in fall, 50% chance before
October 8

The last 15 years (2006–2020 normals)

Typical last frost May 14 (1 day later than the 30-year normal), typical first fall frost September 30 (1 day later). Frost-free season 136 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 Partoun: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 5, 20% May 29, 30% May 21, 40% May 17, 50% May 13, 60% May 9, 70% May 5, 80% May 2, 90% April 28. Observed last spring frost in recent years: 2021 May 24, 2022 May 24, 2023 May 5, 2024 May 21, 2025 May 2, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 5May 13Apr 282021: May 242022: May 242023: May 52024: May 212025: May 22026: May 20Fall at Partoun: chance of a frost before this dateFall, chance of a frost before the date: 10% September 16, 20% September 21, 30% September 24, 40% September 26, 50% September 29, 60% October 1, 70% October 4, 80% October 7, 90% October 11. Observed first fall frost in recent years: 2021 September 30, 2022 October 2, 2023 October 13, 2024 October 19, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 16Sep 29Oct 112021: September 302022: October 22023: October 132024: October 192025: October 7
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
2021May 24September 30
2022May 24October 2
2023May 5October 13
2024May 21October 19
2025May 2October 7
2026May 20season not over yet

What these dates mean

Planting tender crops on April 28 in Partoun carries a 90 % chance of a light frost and is a gamble for growers. The cautious alternative is the later June 5, when only a 10 % chance of frost remains.

The 50 % date for light frost in spring is May 13; the same probability occurs on September 29 in fall. Those dates represent even odds for a frost, not a guaranteed frost event. For a low-risk schedule, growers rely on the cautious June 5 date to set out tender crops and on September 16 to finish harvesting before a likely frost begins.

Hard frost at 28 °F is more damaging than a light 32 °F frost, so the median hard-frost dates—April 30 in spring and October 8 in fall—are useful reference points for protecting sensitive plants.

How to read the probabilities

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

  • Spring: "10% after June 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 16" 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 Partoun, UTNumbered nearest stations: 1 — Callao, UT — 21 mi; 2 — Ibapah, UT — 29 mi; 3 — Eskdale, UT — 36 mi; 4 — Lages, NV — 49 mi; 5 — McGill, NV — 50 mi.NVUT25 mi · 40 km1. Callao, UT — 21 mi12. Ibapah, UT — 29 mi23. Eskdale, UT — 36 mi34. Lages, NV — 49 mi45. McGill, NV — 50 mi5
  1. Callao, UT 21 mi (33 km)
  2. Ibapah, UT 29 mi (46 km)
  3. Eskdale, UT 36 mi (58 km)
  4. Lages, NV 49 mi (79 km)
  5. McGill, NV 50 mi (80 km)

Sources

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

Station coordinates: 39.6308, -113.8858.