U.S. Frost Dates by Weather Station

NOAA station USC00422385 · Utah

Frost Dates near Coalville, UT

NOAA weather station Echo Dam (USC00422385), Utah · elevation 5470 ft (1667 m) · hardiness zone 5b*

Coalville is the nearest town to the station (3.8 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 16only 1 spring in 10 still has a frost later
  • Typical last frostMay 3050% chance of a frost after it
  • Typical first fall frostSeptember 1850% chance of a frost before it
  • Frost-free season112 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season near Coalville, UTSpring: a frost after May 11 in 9 years out of 10, after May 30 in half of the years, after June 16 in 1 year out of 10. Fall: the first frost comes before September 4 in 1 year out of 10, before September 18 in half of the years, before October 1 in 9 years out of 10. Typical frost-free season: 112 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 30First frost ~Sep 18Frost season near Coalville, UTSpring: a frost after May 11 in 9 years out of 10, after May 30 in half of the years, after June 16 in 1 year out of 10. Fall: the first frost comes before September 4 in 1 year out of 10, before September 18 in half of the years, before October 1 in 9 years out of 10. Typical frost-free season: 112 days.JFMAMJJASONDLast frost ~May 30First frost ~Sep 18
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 16September 4
50% (typical)May 30September 18
90% (likely)May 11October 1
Frost-free season (32°F, 50% chance)
112 days
Hard frost (28°F), last in spring, 50% chance after
May 10
Hard frost (28°F), first in fall, 50% chance before
October 1

The last 15 years (2006–2020 normals)

Typical last frost May 30 (same as the 30-year normal), typical first fall frost September 21 (3 days later). Frost-free season 115 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 Coalville: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 16, 20% June 10, 30% June 5, 40% June 1, 50% May 30, 60% May 26, 70% May 22, 80% May 17, 90% May 11. Observed last spring frost in recent years: 2021 May 27, 2022 May 24, 2023 May 7, 2024 June 17, 2025 May 20, 2026 May 23.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 16May 30May 112021: May 272022: May 242023: May 72024: June 172025: May 202026: May 23Fall near Coalville: chance of a frost before this dateFall, chance of a frost before the date: 10% September 4, 20% September 9, 30% September 13, 40% September 15, 50% September 18, 60% September 21, 70% September 24, 80% September 27, 90% October 1. Observed first fall frost in recent years: 2021 September 20, 2022 October 10, 2023 September 22, 2024 October 22, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 4Sep 18Oct 12021: September 202022: October 102023: September 222024: October 222025: 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 27September 20
2022May 24October 10
2023May 7September 22
2024June 17October 22
2025May 20October 7
2026May 23season not over yet

What these dates mean

June 16 is the cautious spring date for the Coalville area; with only a 10 % chance of a light frost later, it marks the earliest day a gardener can reasonably set out tender crops. Anything earlier, such as the 90 % chance on May 11, is a gamble.

The 50% spring date of May 30 and the 50% fall date of September 18 each represent an even-odds point for a light frost, meaning a gardener has a fifty-fifty chance of a frost later than the spring date or earlier than the fall date. The median hard-frost dates are May 10 in spring and October 1 in fall; these indicate when a 28 °F frost is equally likely to have occurred or not.

September 4 is the cautious fall date, with only a 10 % chance that a light frost has arrived earlier, so it is the safest day to finish harvesting tender crops. A hard frost at 28 °F can damage plants that would 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 June 16" 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 4" 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 Coalville, UTNumbered nearest stations: 1 — near Silver Summit, UT — 12 mi; 2 — near Bountiful, UT — 22 mi; 3 — Kamas, UT — 24 mi; 4 — Alta, UT — 28 mi; 5 — near Ogden, UT — 29 mi.WY25 mi · 40 km1. near Silver Summit, UT — 12 mi12. near Bountiful, UT — 22 mi23. Kamas, UT — 24 mi34. Alta, UT — 28 mi45. near Ogden, UT — 29 mi5
  1. near Silver Summit, UT 12 mi (20 km)
  2. near Bountiful, UT 22 mi (36 km)
  3. Kamas, UT 24 mi (38 km)
  4. Alta, UT 28 mi (45 km)
  5. near Ogden, UT 29 mi (47 km)

Sources

* Hardiness zone 5b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 40.9656, -111.4336.