U.S. Frost Dates by Weather Station

NOAA station USC00427260 · Utah

Frost Dates near Richfield, UT

NOAA weather station Richfield Radio KSVC (USC00427260), Utah · elevation 5285 ft (1611 m) · hardiness zone 6a*

Richfield is the nearest town to the station (0.8 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter June 7only 1 spring in 10 still has a frost later
  • Typical last frostMay 2150% chance of a frost after it
  • Typical first fall frostSeptember 2450% chance of a frost before it
  • Frost-free season125 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season near Richfield, UTSpring: a frost after May 4 in 9 years out of 10, after May 21 in half of the years, after June 7 in 1 year out of 10. Fall: the first frost comes before September 12 in 1 year out of 10, before September 24 in half of the years, before October 6 in 9 years out of 10. Typical frost-free season: 125 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 21First frost ~Sep 24Frost season near Richfield, UTSpring: a frost after May 4 in 9 years out of 10, after May 21 in half of the years, after June 7 in 1 year out of 10. Fall: the first frost comes before September 12 in 1 year out of 10, before September 24 in half of the years, before October 6 in 9 years out of 10. Typical frost-free season: 125 days.JFMAMJJASONDLast frost ~May 21First frost ~Sep 24
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 7September 12
50% (typical)May 21September 24
90% (likely)May 4October 6
Frost-free season (32°F, 50% chance)
125 days
Hard frost (28°F), last in spring, 50% chance after
May 7
Hard frost (28°F), first in fall, 50% chance before
October 4

The last 15 years (2006–2020 normals)

Typical last frost May 20 (1 day earlier than the 30-year normal), typical first fall frost September 26 (2 days later). Frost-free season 126 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 near Richfield: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 7, 20% June 2, 30% May 29, 40% May 25, 50% May 21, 60% May 17, 70% May 13, 80% May 10, 90% May 4. Observed last spring frost in recent years: 2021 May 25, 2022 June 1, 2023 May 12, 2024 May 22, 2025 May 21, 2026 May 21.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 7May 21May 42021: May 252022: June 12023: May 122024: May 222025: May 212026: May 21Fall near Richfield: chance of a frost before this dateFall, chance of a frost before the date: 10% September 12, 20% September 17, 30% September 20, 40% September 22, 50% September 24, 60% September 27, 70% September 29, 80% October 2, 90% October 6. Observed first fall frost in recent years: 2021 September 21, 2022 October 13, 2023 September 25, 2024 October 15, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 12Sep 24Oct 62021: September 212022: October 132023: September 252024: October 152025: October 6
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 25September 21
2022June 1October 13
2023May 12September 25
2024May 22October 15
2025May 21October 6
2026May 21season not over yet

What these dates mean

The 125-day span between the two 32 °F 50% dates—May 21 and September 24—captures the period when light frosts are equally likely to have occurred or not, and it also contains the median hard-frost dates, May 7 and October 4. Those 50% dates are not frost dates; they simply mark the point at which a gardener faces even odds of a frost having happened.

For a cautious spring plan, the June 7 date carries a 10 % chance of a light frost later, making it the recommended day to set out tender crops, while the May 4 date carries a 90 % chance and is a gamble. In the fall, September 12 is the cautious date with a 10 % chance of a light frost earlier, suitable for finishing tender harvests, whereas October 6 carries a 90 % chance and is risky. A hard frost at 28 °F matters more than a light frost at 32 °F because it can damage or kill plants that survive milder temperatures.

How to read the probabilities

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

  • Spring: "10% after June 7" 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 12" 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 Richfield, UTNumbered nearest stations: 1 — Salina, UT — 37 mi; 2 — Manti, UT — 42 mi; 3 — Black Rock, UT — 47 mi; 4 — Deseret, UT — 48 mi; 5 — Ephraim, UT — 49 mi.UT25 mi · 40 km1. Salina, UT — 37 mi12. Manti, UT — 42 mi23. Black Rock, UT — 47 mi34. Deseret, UT — 48 mi45. Ephraim, UT — 49 mi5
  1. Salina, UT 37 mi (60 km)
  2. Manti, UT 42 mi (67 km)
  3. Black Rock, UT 47 mi (76 km)
  4. Deseret, UT 48 mi (77 km)
  5. Ephraim, UT 49 mi (78 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: 38.7617, -112.0778.