U.S. Frost Dates by Weather Station

NOAA station USC00053541 · Colorado

Frost Dates for Great Sand Dunes National Park & Preserve, CO

NOAA weather station Great Sand Dunes National Park & Preserve (USC00053541), Colorado · elevation 8183 ft (2494 m) · hardiness zone 6a*

  • Lower-risk planting dateafter June 3only 1 spring in 10 still has a frost later
  • Typical last frostMay 2150% chance of a frost after it
  • Typical first fall frostOctober 150% chance of a frost before it
  • Frost-free season131 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Great Sand Dunes National Park & Preserve, COSpring: a frost after May 9 in 9 years out of 10, after May 21 in half of the years, after June 3 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 14 in 9 years out of 10. Typical frost-free season: 131 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 21First frost ~Oct 1Frost season at Great Sand Dunes National Park & Preserve, COSpring: a frost after May 9 in 9 years out of 10, after May 21 in half of the years, after June 3 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 14 in 9 years out of 10. Typical frost-free season: 131 days.JFMAMJJASONDLast frost ~May 21First 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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 3September 19
50% (typical)May 21October 1
90% (likely)May 9October 14
Frost-free season (32°F, 50% chance)
131 days
Hard frost (28°F), last in spring, 50% chance after
May 10
Hard frost (28°F), first in fall, 50% chance before
October 10

The last 15 years (2006–2020 normals)

Typical last frost May 22 (1 day later than the 30-year normal), typical first fall frost October 3 (2 days later). Frost-free season 132 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 Great Sand Dunes National Park & Preserve: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 3, 20% May 30, 30% May 26, 40% May 23, 50% May 21, 60% May 18, 70% May 16, 80% May 13, 90% May 9. Observed last spring frost in recent years: 2021 May 18, 2022 May 30, 2023 May 12, 2024 May 22, 2025 May 21, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 3May 21May 92021: May 182022: May 302023: May 122024: May 222025: May 212026: May 7Fall at Great Sand Dunes National Park & Preserve: chance of a frost before this dateFall, chance of a frost before the date: 10% September 19, 20% September 23, 30% September 26, 40% September 29, 50% October 1, 60% October 4, 70% October 6, 80% October 9, 90% October 14. Observed first fall frost in recent years: 2021 October 2, 2022 October 17, 2023 October 13, 2024 October 22, 2025 October 5.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 19Oct 1Oct 142021: October 22022: October 172023: October 132024: October 222025: October 5
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 18October 2
2022May 30October 17
2023May 12October 13
2024May 22October 22
2025May 21October 5
2026May 7season not over yet

What these dates mean

Planting tender crops on the early spring date of May 9 carries a 90 % chance that a light frost will still occur later, making it a gamble for growers in Great Sand Dunes National Park & Preserve. The cautious spring date is June 3, when only a 10 % chance of frost remains.

For gardeners, the 50 % dates – May 21 for spring and October 1 for fall – mark the point at which a light frost is equally likely to have happened or not, providing a statistical midpoint rather than a frost event. A cautious fall plan uses September 19, the date with only a 10 % chance that a light frost has already arrived. The hard-frost median dates are May 10 and October 10; a hard frost at 28 °F can kill tender crops that 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 3" 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 Great Sand Dunes National Park & Preserve, CONumbered nearest stations: 1 — Sheep Mountain, CO — 15 mi; 2 — Westcliffe, CO — 28 mi; 3 — near Alamosa, CO — 28 mi; 4 — Monte Vista, CO — 38 mi; 5 — Walsenburg, CO — 40 mi.25 mi · 40 km1. Sheep Mountain, CO — 15 mi12. Westcliffe, CO — 28 mi23. near Alamosa, CO — 28 mi34. Monte Vista, CO — 38 mi45. Walsenburg, CO — 40 mi5
  1. Sheep Mountain, CO 15 mi (24 km)
  2. Westcliffe, CO 28 mi (44 km)
  3. near Alamosa, CO 28 mi (45 km)
  4. Monte Vista, CO 38 mi (62 km)
  5. Walsenburg, CO 40 mi (64 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: 37.7333, -105.5119.