U.S. Frost Dates by Weather Station

NOAA station USC00422864 · Utah

Frost Dates for Flaming Gorge, UT

NOAA weather station Flaming Gorge (USC00422864), Utah · elevation 6244 ft (1903 m) · hardiness zone 5b*

  • Lower-risk planting dateafter June 10only 1 spring in 10 still has a frost later
  • Typical last frostMay 2650% chance of a frost after it
  • Typical first fall frostSeptember 2350% chance of a frost before it
  • Frost-free season120 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Flaming Gorge, UTSpring: a frost after May 9 in 9 years out of 10, after May 26 in half of the years, after June 10 in 1 year out of 10. Fall: the first frost comes before September 9 in 1 year out of 10, before September 23 in half of the years, before October 4 in 9 years out of 10. Typical frost-free season: 120 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 26First frost ~Sep 23Frost season at Flaming Gorge, UTSpring: a frost after May 9 in 9 years out of 10, after May 26 in half of the years, after June 10 in 1 year out of 10. Fall: the first frost comes before September 9 in 1 year out of 10, before September 23 in half of the years, before October 4 in 9 years out of 10. Typical frost-free season: 120 days.JFMAMJJASONDLast frost ~May 26First frost ~Sep 23
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 10September 9
50% (typical)May 26September 23
90% (likely)May 9October 4
Frost-free season (32°F, 50% chance)
120 days
Hard frost (28°F), last in spring, 50% chance after
May 10
Hard frost (28°F), first in fall, 50% chance before
October 3

The last 15 years (2006–2020 normals)

Typical last frost May 25 (1 day earlier than the 30-year normal), typical first fall frost September 27 (4 days later). Frost-free season 124 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 Flaming Gorge: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 10, 20% June 5, 30% June 2, 40% May 29, 50% May 26, 60% May 22, 70% May 19, 80% May 15, 90% May 9. Observed last spring frost in recent years: 2021 May 25, 2022 June 15, 2023 May 10, 2024 May 27, 2025 June 23, 2026 June 11.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 10May 26May 92021: May 252022: June 152023: May 102024: May 272025: June 232026: June 11Fall at Flaming Gorge: chance of a frost before this dateFall, chance of a frost before the date: 10% September 9, 20% September 13, 30% September 17, 40% September 20, 50% September 23, 60% September 25, 70% September 28, 80% October 1, 90% October 4. Observed first fall frost in recent years: 2021 September 14, 2022 October 6, 2023 September 21, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 9Sep 23Oct 42021: September 142022: October 62023: September 212025: 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 25September 14
2022June 15October 6
2023May 10September 21
2024May 27incomplete record
2025June 23October 7
2026June 11season not over yet

What these dates mean

Setting out tender crops on the early spring date of May 9 carries a 90 % chance of a frost later, so it is a gamble for gardeners in Flaming Gorge.

The 50 % date in spring is May 26, meaning there is a 50 % chance of a frost later than this date, while the 50 % date in fall is September 23, meaning there is a 50 % chance of a frost earlier than this date. The hard-frost median dates are May 10 and October 3; a hard frost reaches 28 °F, which can injure plants that would survive a light 32 °F frost.

A cautious plan uses the June 10 date, which has a 10 % chance of a frost later, for setting out tender crops in spring, and the September 9 date, which has a 10 % chance of a frost earlier, for finishing harvests in fall.

How to read the probabilities

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

  • Spring: "10% after June 10" 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 9" 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 Flaming Gorge, UTNumbered nearest stations: 1 — Jensen, UT — 40 mi; 2 — Neola, UT — 49 mi; 3 — Rock Springs, WY — 49 mi; 4 — near Roosevelt, UT — 53 mi; 5 — Ouray, UT — 56 mi.WYCO25 mi · 40 km1. Jensen, UT — 40 mi12. Neola, UT — 49 mi23. Rock Springs, WY — 49 mi34. near Roosevelt, UT — 53 mi45. Ouray, UT — 56 mi5
  1. Jensen, UT 40 mi (64 km)
  2. Neola, UT 49 mi (79 km)
  3. Rock Springs, WY 49 mi (80 km)
  4. near Roosevelt, UT 53 mi (85 km)
  5. Ouray, UT 56 mi (91 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: 40.9317, -109.4117.