U.S. Frost Dates by Weather Station

NOAA station USC00056832 · Colorado

Frost Dates for Rangely, CO

NOAA weather station Rangely 1 E (USC00056832), Colorado · elevation 5277 ft (1608 m) · hardiness zone 5a*

  • Lower-risk planting dateafter June 2only 1 spring in 10 still has a frost later
  • Typical last frostMay 1550% chance of a frost after it
  • Typical first fall frostOctober 150% chance of a frost before it
  • Frost-free season136 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Rangely, COSpring: a frost after May 2 in 9 years out of 10, after May 15 in half of the years, after June 2 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 1 in half of the years, before October 12 in 9 years out of 10. Typical frost-free season: 136 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 15First frost ~Oct 1Frost season at Rangely, COSpring: a frost after May 2 in 9 years out of 10, after May 15 in half of the years, after June 2 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 1 in half of the years, before October 12 in 9 years out of 10. Typical frost-free season: 136 days.JFMAMJJASONDLast frost ~May 15First frost ~Oct 1
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 2September 19
50% (typical)May 15October 1
90% (likely)May 2October 12
Frost-free season (32°F, 50% chance)
136 days
Hard frost (28°F), last in spring, 50% chance after
May 3
Hard frost (28°F), first in fall, 50% chance before
October 10

The last 15 years (2006–2020 normals)

Typical last frost May 13 (2 days earlier than the 30-year normal), typical first fall frost October 3 (2 days later). Frost-free season 141 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 Rangely: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 2, 20% May 27, 30% May 23, 40% May 18, 50% May 15, 60% May 13, 70% May 10, 80% May 6, 90% May 2. Observed last spring frost in recent years: 2021 May 5, 2022 May 21, 2023 April 29, 2024 May 25, 2025 April 20, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 2May 15May 22021: May 52022: May 212023: April 292024: May 252025: April 202026: May 19Fall at Rangely: chance of a frost before this dateFall, chance of a frost before the date: 10% September 19, 20% September 23, 30% September 25, 40% September 28, 50% October 1, 60% October 3, 70% October 5, 80% October 8, 90% October 12. Observed first fall frost in recent years: 2021 October 13, 2022 October 15, 2023 October 4, 2024 October 25, 2025 October 18.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 19Oct 1Oct 122021: October 132022: October 152023: October 42024: October 252025: October 18
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 5October 13
2022May 21October 15
2023April 29October 4
2024May 25October 25
2025April 20October 18
2026May 19season not over yet

What these dates mean

The 136 days between the 50% dates in Rangely—May 15 and October 1—frame the main growing window.

The 50% date in spring is May 15, with a 50% chance of a light frost later than this date; the 50% date in fall is October 1, with a 50% chance of a light frost earlier than this date. A cautious plan sets out tender crops on the June 2 date, which carries only a 10% chance of a later light frost, and finishes harvesting tender crops by the September 19 date, which carries only a 10% chance of an earlier light frost.

Hard-frost thresholds are lower; the 50% hard-frost dates are May 3 and October 10, and a hard frost can damage plants more severely than a light frost because it occurs at 28 °F rather than 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 2" 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 19" 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 Rangely, CONumbered nearest stations: 1 — Jensen, UT — 36 mi; 2 — Altenbern, CO — 46 mi; 3 — Meeker, CO — 46 mi; 4 — Ouray, UT — 46 mi; 5 — Maybell, CO — 46 mi.COUT25 mi · 40 km1. Jensen, UT — 36 mi12. Altenbern, CO — 46 mi23. Meeker, CO — 46 mi34. Ouray, UT — 46 mi45. Maybell, CO — 46 mi5
  1. Jensen, UT 36 mi (57 km)
  2. Altenbern, CO 46 mi (74 km)
  3. Meeker, CO 46 mi (74 km)
  4. Ouray, UT 46 mi (74 km)
  5. Maybell, CO 46 mi (75 km)

Sources

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

Station coordinates: 40.0889, -108.7728.