U.S. Frost Dates by Weather Station

NOAA station USC00057572 · Colorado

Frost Dates for Sheep Mountain, CO

NOAA weather station Sheep Mountain (USC00057572), Colorado · elevation 7744 ft (2360 m) · hardiness zone 6a*

  • Lower-risk planting dateafter June 10only 1 spring in 10 still has a frost later
  • Typical last frostMay 2750% chance of a frost after it
  • Typical first fall frostSeptember 2550% chance of a frost before it
  • Frost-free season119 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Sheep Mountain, COSpring: a frost after May 12 in 9 years out of 10, after May 27 in half of the years, after June 10 in 1 year out of 10. Fall: the first frost comes before September 11 in 1 year out of 10, before September 25 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 119 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 27First frost ~Sep 25Frost season at Sheep Mountain, COSpring: a frost after May 12 in 9 years out of 10, after May 27 in half of the years, after June 10 in 1 year out of 10. Fall: the first frost comes before September 11 in 1 year out of 10, before September 25 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 119 days.JFMAMJJASONDLast frost ~May 27First frost ~Sep 25
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 10September 11
50% (typical)May 27September 25
90% (likely)May 12October 8
Frost-free season (32°F, 50% chance)
119 days
Hard frost (28°F), last in spring, 50% chance after
May 13
Hard frost (28°F), first in fall, 50% chance before
October 4

The last 15 years (2006–2020 normals)

Typical last frost May 26 (1 day earlier than the 30-year normal), typical first fall frost October 1 (6 days later). Frost-free season 127 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 Sheep Mountain: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 10, 20% June 4, 30% June 1, 40% May 30, 50% May 27, 60% May 23, 70% May 20, 80% May 17, 90% May 12.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 10May 27May 12Fall at Sheep Mountain: chance of a frost before this dateFall, chance of a frost before the date: 10% September 11, 20% September 16, 30% September 20, 40% September 23, 50% September 25, 60% September 28, 70% October 1, 80% October 3, 90% October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 11Sep 25Oct 8
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.

What these dates mean

Setting out tender crops on the early spring date, May 12, carries a 90% chance of a frost and is therefore a gamble at Sheep Mountain. The cautious spring date for tender crops is June 10, when only a 10% chance of a frost later than that day remains.

The 50% spring date is May 27; there is a 50% chance of a frost later than this date. In autumn the cautious date to finish harvesting tender crops is September 11, with a 10% chance of a frost earlier than that day, while the 50% fall date is September 25 and a 50% chance of a frost earlier than it occurs. The hard-frost 50% dates are May 13 and October 4; hard frosts at 28 °F can damage plants that survive a light frost at 32 °F, making them a greater threat.

Gardeners can use the cautious dates to reduce risk while the 50% dates indicate the point at which frost likelihood is evenly split.

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 11" 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 Sheep Mountain, CONumbered nearest stations: 1 — Great Sand Dunes National Park & Preserve, CO — 15 mi; 2 — Walsenburg, CO — 25 mi; 3 — Westcliffe, CO — 31 mi; 4 — near Alamosa, CO — 39 mi; 5 — Canon City, CO — 51 mi.CO25 mi · 40 km1. Great Sand Dunes National Park & Preserve, CO — 15 mi12. Walsenburg, CO — 25 mi23. Westcliffe, CO — 31 mi34. near Alamosa, CO — 39 mi45. Canon City, CO — 51 mi5
  1. Great Sand Dunes National Park & Preserve, CO 15 mi (24 km)
  2. Walsenburg, CO 25 mi (40 km)
  3. Westcliffe, CO 31 mi (51 km)
  4. near Alamosa, CO 39 mi (63 km)
  5. Canon City, CO 51 mi (83 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: 37.715, -105.2353.