U.S. Frost Dates by Weather Station

NOAA station USC00052790 · Colorado

Frost Dates for Evergreen, CO

NOAA weather station Evergreen (USC00052790), Colorado · elevation 6985 ft (2129 m) · hardiness zone 5b*

  • Lower-risk planting dateafter June 10only 1 spring in 10 still has a frost later
  • Typical last frostMay 2350% chance of a frost after it
  • Typical first fall frostSeptember 2250% chance of a frost before it
  • Frost-free season118 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Evergreen, COSpring: a frost after May 9 in 9 years out of 10, after May 23 in half of the years, after June 10 in 1 year out of 10. Fall: the first frost comes before September 6 in 1 year out of 10, before September 22 in half of the years, before October 3 in 9 years out of 10. Typical frost-free season: 118 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 23First frost ~Sep 22Frost season at Evergreen, COSpring: a frost after May 9 in 9 years out of 10, after May 23 in half of the years, after June 10 in 1 year out of 10. Fall: the first frost comes before September 6 in 1 year out of 10, before September 22 in half of the years, before October 3 in 9 years out of 10. Typical frost-free season: 118 days.JFMAMJJASONDLast frost ~May 23First frost ~Sep 22
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 10September 6
50% (typical)May 23September 22
90% (likely)May 9October 3
Frost-free season (32°F, 50% chance)
118 days
Hard frost (28°F), last in spring, 50% chance after
May 9
Hard frost (28°F), first in fall, 50% chance before
October 2

The last 15 years (2006–2020 normals)

Typical last frost May 25 (2 days later than the 30-year normal), typical first fall frost September 27 (5 days later). Frost-free season 122 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 Evergreen: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 10, 20% June 2, 30% May 29, 40% May 26, 50% May 23, 60% May 20, 70% May 17, 80% May 14, 90% May 9. Observed last spring frost in recent years: 2021 May 25, 2022 May 31, 2023 May 9, 2024 May 25, 2026 May 22.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 10May 23May 92021: May 252022: May 312023: May 92024: May 252026: May 22Fall at Evergreen: chance of a frost before this dateFall, chance of a frost before the date: 10% September 6, 20% September 13, 30% September 16, 40% September 19, 50% September 22, 60% September 24, 70% September 27, 80% September 30, 90% October 3. Observed first fall frost in recent years: 2021 September 22, 2022 October 8, 2023 September 16, 2024 October 23.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 6Sep 22Oct 32021: September 222022: October 82023: September 162024: October 23
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 25September 22
2022May 31October 8
2023May 9September 16
2024May 25October 23
2025incomplete recordincomplete record
2026May 22season not over yet

What these dates mean

Setting out tender crops on the early spring date of May 9 carries a 90 % chance of a light frost, making it a gamble for growers in Evergreen.

The 50% date is May 23, with a 50 % chance of a light frost later than this date, and the 50% date is September 22, with a 50 % chance of a light frost earlier than this date. A cautious planting plan would wait until the June 10 date, which has only a 10 % chance of a later light frost, while a cautious harvest finish would aim for September 6, which carries only a 10 % chance of an earlier light frost. The hard-frost 50% dates are May 9 and October 2, each indicating an even chance of a hard frost.

Hard frosts at 28 °F can damage plant tissue that survives a 32 °F light frost, so they are a greater risk.

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 6" 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 Evergreen, CONumbered nearest stations: 1 — Wheat Ridge, CO — 14 mi; 2 — near Coal Creek, CO — 18 mi; 3 — Bailey, CO — 18 mi; 4 — Georgetown, CO — 21 mi; 5 — Cabin Creek, CO — 21 mi.25 mi · 40 km1. Wheat Ridge, CO — 14 mi12. near Coal Creek, CO — 18 mi23. Bailey, CO — 18 mi34. Georgetown, CO — 21 mi45. Cabin Creek, CO — 21 mi5
  1. Wheat Ridge, CO 14 mi (23 km)
  2. near Coal Creek, CO 18 mi (29 km)
  3. Bailey, CO 18 mi (29 km)
  4. Georgetown, CO 21 mi (34 km)
  5. Cabin Creek, CO 21 mi (34 km)

Sources

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

Station coordinates: 39.6381, -105.315.