U.S. Frost Dates by Weather Station

NOAA station USC00055934 · Colorado

Frost Dates for New Raymer, CO

NOAA weather station New Raymer 21 N (USC00055934), Colorado · elevation 5180 ft (1579 m) · hardiness zone 5a*

  • Lower-risk planting dateafter June 2only 1 spring in 10 still has a frost later
  • Typical last frostMay 1850% chance of a frost after it
  • Typical first fall frostSeptember 2950% chance of a frost before it
  • Frost-free season133 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at New Raymer, COSpring: a frost after May 5 in 9 years out of 10, after May 18 in half of the years, after June 2 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 133 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 18First frost ~Sep 29Frost season at New Raymer, COSpring: a frost after May 5 in 9 years out of 10, after May 18 in half of the years, after June 2 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 133 days.JFMAMJJASONDLast frost ~May 18First frost ~Sep 29
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 2September 15
50% (typical)May 18September 29
90% (likely)May 5October 11
Frost-free season (32°F, 50% chance)
133 days
Hard frost (28°F), last in spring, 50% chance after
May 6
Hard frost (28°F), first in fall, 50% chance before
October 8

The last 15 years (2006–2020 normals)

Typical last frost May 14 (4 days earlier than the 30-year normal), typical first fall frost October 1 (2 days later). Frost-free season 137 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 New Raymer: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 2, 20% May 29, 30% May 24, 40% May 21, 50% May 18, 60% May 15, 70% May 12, 80% May 9, 90% May 5. Observed last spring frost in recent years: 2022 May 26, 2023 May 6, 2024 May 23, 2025 May 22, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 2May 18May 52022: May 262023: May 62024: May 232025: May 222026: May 19Fall at New Raymer: chance of a frost before this dateFall, chance of a frost before the date: 10% September 15, 20% September 21, 30% September 24, 40% September 26, 50% September 29, 60% October 1, 70% October 4, 80% October 7, 90% October 11. Observed first fall frost in recent years: 2022 October 12, 2023 October 7, 2024 October 6, 2025 October 19.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 15Sep 29Oct 112022: October 122023: October 72024: October 62025: October 19
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
2021no datano data
2022May 26October 12
2023May 6October 7
2024May 23October 6
2025May 22October 19
2026May 19season not over yet

What these dates mean

The 133 days between the 50% dates in New Raymer mark the core period between the median light-frost risk points. The 50% date for spring light frost is May 18 and the 50% date for fall light frost is September 29; on each of those days the chance of a 32 °F frost is exactly fifty-fifty. A hard-frost 50% date occurs on May 6 in spring and October 8 in fall, indicating when a 28 °F frost is equally likely to have happened or not.

In spring the cautious date for setting out tender crops is June 2, when there is only a ten-percent chance of a light frost later, while May 5 carries a ninety-percent chance and is a gamble. In fall the cautious date to finish harvesting tender crops is September 15, with a ten-percent chance of a light frost earlier, and October 11 is a gamble with a ninety-percent chance. A hard frost at 28 °F can injure plants that survive a light frost at 32 °F, so the hard-frost threshold is more critical.

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 15" 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 New Raymer, CONumbered nearest stations: 1 — Harrisburg, NE — 49 mi; 2 — Cheyenne, WY — 51 mi; 3 — Leroy, CO — 54 mi; 4 — near Greeley, CO — 57 mi; 5 — Akron Washington County Airport, CO — 63 mi.CONEWY25 mi · 40 km1. Harrisburg, NE — 49 mi12. Cheyenne, WY — 51 mi23. Leroy, CO — 54 mi34. near Greeley, CO — 57 mi45. Akron Washington County Airport, CO — 63 mi5
  1. Harrisburg, NE 49 mi (78 km)
  2. Cheyenne, WY 51 mi (82 km)
  3. Leroy, CO 54 mi (87 km)
  4. near Greeley, CO 57 mi (92 km)
  5. Akron Washington County Airport, CO 63 mi (101 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: 40.9319, -103.8678.