U.S. Frost Dates by Weather Station

NOAA station USC00422578 · Utah

Frost Dates for Ephraim, UT

NOAA weather station Ephraim (USC00422578), Utah · elevation 5498 ft (1676 m) · hardiness zone 6a*

  • Lower-risk planting dateafter June 15only 1 spring in 10 still has a frost later
  • Typical last frostMay 2850% chance of a frost after it
  • Typical first fall frostSeptember 2050% chance of a frost before it
  • Frost-free season113 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Ephraim, UTSpring: a frost after May 12 in 9 years out of 10, after May 28 in half of the years, after June 15 in 1 year out of 10. Fall: the first frost comes before September 5 in 1 year out of 10, before September 20 in half of the years, before October 1 in 9 years out of 10. Typical frost-free season: 113 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 28First frost ~Sep 20Frost season at Ephraim, UTSpring: a frost after May 12 in 9 years out of 10, after May 28 in half of the years, after June 15 in 1 year out of 10. Fall: the first frost comes before September 5 in 1 year out of 10, before September 20 in half of the years, before October 1 in 9 years out of 10. Typical frost-free season: 113 days.JFMAMJJASONDLast frost ~May 28First frost ~Sep 20
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 15September 5
50% (typical)May 28September 20
90% (likely)May 12October 1
Frost-free season (32°F, 50% chance)
113 days
Hard frost (28°F), last in spring, 50% chance after
May 12
Hard frost (28°F), first in fall, 50% chance before
September 29

The last 15 years (2006–2020 normals)

Typical last frost May 26 (2 days earlier than the 30-year normal), typical first fall frost September 22 (2 days later). Frost-free season 117 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 Ephraim: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 15, 20% June 8, 30% June 4, 40% June 1, 50% May 28, 60% May 24, 70% May 21, 80% May 17, 90% May 12. Observed last spring frost in recent years: 2021 June 10, 2022 June 14, 2023 May 10, 2024 May 23, 2025 May 20, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 15May 28May 122021: June 102022: June 142023: May 102024: May 232025: May 202026: May 20Fall at Ephraim: chance of a frost before this dateFall, chance of a frost before the date: 10% September 5, 20% September 10, 30% September 14, 40% September 17, 50% September 20, 60% September 23, 70% September 25, 80% September 28, 90% October 1. Observed first fall frost in recent years: 2021 September 20, 2022 October 9, 2023 September 22, 2024 September 30, 2025 October 5.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 5Sep 20Oct 12021: September 202022: October 92023: September 222024: September 302025: October 5
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
2021June 10September 20
2022June 14October 9
2023May 10September 22
2024May 23September 30
2025May 20October 5
2026May 20season not over yet

What these dates mean

September 5 is the cautious fall date in Ephraim for finishing the harvest; there is only a 10 % chance that a light frost has arrived earlier, making it the point by which tender crops should be pulled in.

The 50% light-frost dates are May 28 in spring and September 20 in fall; each marks an even odds point for gardeners, meaning a 50 % chance of a frost later than May 28 or earlier than September 20. For hard frosts, the 50 % dates are May 12 and September 29, indicating when a 28 °F frost is equally likely to have occurred or not.

A cautious planting plan uses the June 15 spring date, which carries a 10 % chance of a later frost, and the September 5 fall date, which carries a 10 % chance of an earlier frost. Because a hard frost at 28 °F can damage plant tissue that a light frost at 32 °F may not, it represents a more serious risk for tender crops.

How to read the probabilities

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

  • Spring: "10% after June 15" 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 5" 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 Ephraim, UTNumbered nearest stations: 1 — Manti, UT — 7 mi; 2 — Nephi, UT — 27 mi; 3 — Scofield-Skyline Mine, UT — 31 mi; 4 — Ferron, UT — 31 mi; 5 — Salina, UT — 32 mi.25 mi · 40 km1. Manti, UT — 7 mi12. Nephi, UT — 27 mi23. Scofield-Skyline Mine, UT — 31 mi34. Ferron, UT — 31 mi45. Salina, UT — 32 mi5
  1. Manti, UT 7 mi (11 km)
  2. Nephi, UT 27 mi (44 km)
  3. Scofield-Skyline Mine, UT 31 mi (50 km)
  4. Ferron, UT 31 mi (50 km)
  5. Salina, UT 32 mi (52 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: 39.3583, -111.5992.