U.S. Frost Dates by Weather Station

NOAA station USW00023070 · Colorado

Frost Dates near Trinidad, CO

NOAA weather station Trinidad Perry Stokes Airport (USW00023070), Colorado · elevation 5741 ft (1750 m) · hardiness zone 6a*

Trinidad is the nearest town to the station (11.0 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter May 19only 1 spring in 10 still has a frost later
  • Typical last frostMay 450% chance of a frost after it
  • Typical first fall frostOctober 950% chance of a frost before it
  • Frost-free season156 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season near Trinidad, COSpring: a frost after April 20 in 9 years out of 10, after May 4 in half of the years, after May 19 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 9 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 156 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 4First frost ~Oct 9Frost season near Trinidad, COSpring: a frost after April 20 in 9 years out of 10, after May 4 in half of the years, after May 19 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 9 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 156 days.JFMAMJJASONDLast frost ~May 4First frost ~Oct 9
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)May 19September 28
50% (typical)May 4October 9
90% (likely)April 20October 21
Frost-free season (32°F, 50% chance)
156 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
October 18

The last 15 years (2006–2020 normals)

Typical last frost May 5 (1 day later than the 30-year normal), typical first fall frost October 12 (3 days later). Frost-free season 158 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 near Trinidad: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 19, 20% May 12, 30% May 9, 40% May 6, 50% May 4, 60% May 2, 70% April 29, 80% April 26, 90% April 20. Observed last spring frost in recent years: 2021 April 29, 2022 May 21, 2023 April 28, 2024 May 8, 2025 April 29, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 19May 4Apr 202021: April 292022: May 212023: April 282024: May 82025: April 292026: May 7Fall near Trinidad: chance of a frost before this dateFall, chance of a frost before the date: 10% September 28, 20% October 2, 30% October 4, 40% October 7, 50% October 9, 60% October 11, 70% October 14, 80% October 17, 90% October 21. Observed first fall frost in recent years: 2021 October 15, 2022 October 13, 2023 October 13, 2024 October 30, 2025 October 18.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 28Oct 9Oct 212021: October 152022: October 132023: October 132024: October 302025: 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
2021April 29October 15
2022May 21October 13
2023April 28October 13
2024May 8October 30
2025April 29October 18
2026May 7season not over yet

What these dates mean

The 156 days between the 32 °F 50 % dates of May 4 and October 9 in the Trinidad area define the period for most tender-crop planting, growth and harvest.

For a cautious spring plan, the 10 % chance date of May 19 is used as the cautious date to set out tender crops, while the 90 % chance date of April 20 would be a gamble. In the fall, the cautious date is September 28, when there is only a 10 % chance that a light frost has arrived, and extending tender crops to October 21 carries a 90 % chance of frost and is risky. The 50 % dates—May 4 in spring and October 9 in fall—each mark a 50 % chance of a frost later (spring) or earlier (fall) and are not themselves frost dates.

A hard frost at 28 °F is more damaging than a light frost at 32 °F, and the median hard-frost dates are April 23 in spring and October 18 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 May 19" 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 28" 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 Trinidad, CONumbered nearest stations: 1 — Raton, NM — 24 mi; 2 — Walsenburg, CO — 36 mi; 3 — Kim 15 NNE, CO — 57 mi; 4 — Kim 10 SSE, CO — 58 mi; 5 — Sheep Mountain, CO — 58 mi.CONM25 mi · 40 km1. Raton, NM — 24 mi12. Walsenburg, CO — 36 mi23. Kim 15 NNE, CO — 57 mi34. Kim 10 SSE, CO — 58 mi45. Sheep Mountain, CO — 58 mi5
  1. Raton, NM 24 mi (39 km)
  2. Walsenburg, CO 36 mi (58 km)
  3. Kim 15 NNE, CO 57 mi (92 km)
  4. Kim 10 SSE, CO 58 mi (93 km)
  5. Sheep Mountain, CO 58 mi (94 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: 37.2622, -104.3378.