U.S. Frost Dates by Weather Station

NOAA station USC00426135 · Utah

Frost Dates for Nephi, UT

NOAA weather station Nephi (USC00426135), Utah · elevation 5146 ft (1569 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 24only 1 spring in 10 still has a frost later
  • Typical last frostMay 650% chance of a frost after it
  • Typical first fall frostOctober 1050% chance of a frost before it
  • Frost-free season156 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Nephi, UTSpring: a frost after April 21 in 9 years out of 10, after May 6 in half of the years, after May 24 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 10 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 156 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 6First frost ~Oct 10Frost season at Nephi, UTSpring: a frost after April 21 in 9 years out of 10, after May 6 in half of the years, after May 24 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 10 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 156 days.JFMAMJJASONDLast frost ~May 6First frost ~Oct 10
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 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 24September 28
50% (typical)May 6October 10
90% (likely)April 21October 24
Frost-free season (32°F, 50% chance)
156 days
Hard frost (28°F), last in spring, 50% chance after
April 21
Hard frost (28°F), first in fall, 50% chance before
October 23

The last 15 years (2006–2020 normals)

Typical last frost May 7 (1 day later than the 30-year normal), typical first fall frost October 11 (1 day later). Frost-free season 157 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 Nephi: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 24, 20% May 18, 30% May 13, 40% May 9, 50% May 6, 60% May 2, 70% April 30, 80% April 27, 90% April 21. Observed last spring frost in recent years: 2022 May 31, 2023 April 26, 2024 May 9, 2025 May 19, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 24May 6Apr 212022: May 312023: April 262024: May 92025: May 192026: May 19Fall at Nephi: chance of a frost before this dateFall, chance of a frost before the date: 10% September 28, 20% October 1, 30% October 4, 40% October 7, 50% October 10, 60% October 13, 70% October 16, 80% October 20, 90% October 24. Observed first fall frost in recent years: 2021 October 13, 2022 October 23, 2023 October 13, 2024 October 18, 2025 October 17.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 28Oct 10Oct 242021: October 132022: October 232023: October 132024: October 182025: October 17
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 13
2022May 31October 23
2023April 26October 13
2024May 9October 18
2025May 19October 17
2026May 19season not over yet

What these dates mean

September 28 is the cautious fall date in Nephi for finishing the harvest, as it carries only a 10 % chance that a light frost has arrived earlier.

The 50% spring light-frost date is May 6; at that point a light frost is equally likely to occur later. Gardeners who wait until the cautious spring date of May 24, which has a 10 % chance of a frost later, reduce the risk when setting out tender crops, while planting on April 21 involves a 90 % chance and is a gamble.

The 50% fall light-frost date is October 10, marking an even chance of a frost earlier. The cautious fall date of September 28 keeps the risk low, whereas planting on October 24 carries a 90 % chance of an earlier frost. Hard-frost median dates are April 21 in spring and October 23 in fall; a hard frost at 28 °F can damage plants that survive 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 24" 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 28" 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 Nephi, UTNumbered nearest stations: 1 — near Santaquin, UT — 17 mi; 2 — Ephraim, UT — 27 mi; 3 — Spanish Fork, UT — 28 mi; 4 — Manti, UT — 33 mi; 5 — Scofield-Skyline Mine, UT — 33 mi.UT25 mi · 40 km1. near Santaquin, UT — 17 mi12. Ephraim, UT — 27 mi23. Spanish Fork, UT — 28 mi34. Manti, UT — 33 mi45. Scofield-Skyline Mine, UT — 33 mi5
  1. near Santaquin, UT 17 mi (28 km)
  2. Ephraim, UT 27 mi (44 km)
  3. Spanish Fork, UT 28 mi (45 km)
  4. Manti, UT 33 mi (53 km)
  5. Scofield-Skyline Mine, UT 33 mi (54 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: 39.7119, -111.8319.