U.S. Frost Dates by Weather Station

NOAA station USC00053553 · Colorado

Frost Dates near Greeley, CO

NOAA weather station Greeley UNC (USC00053553), Colorado · elevation 4715 ft (1437 m) · hardiness zone 5b*

Greeley is the nearest town to the station (1.6 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 14only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 850% chance of a frost before it
  • Frost-free season159 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season near Greeley, COSpring: a frost after April 17 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 8 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 159 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 8Frost season near Greeley, COSpring: a frost after April 17 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 8 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 159 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 8
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 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 14September 26
50% (typical)May 2October 8
90% (likely)April 17October 21
Frost-free season (32°F, 50% chance)
159 days
Hard frost (28°F), last in spring, 50% chance after
April 20
Hard frost (28°F), first in fall, 50% chance before
October 18

The last 15 years (2006–2020 normals)

Typical last frost May 3 (1 day later than the 30-year normal), typical first fall frost October 11 (3 days later). Frost-free season 159 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 Greeley: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 14, 20% May 10, 30% May 7, 40% May 5, 50% May 2, 60% April 30, 70% April 27, 80% April 22, 90% April 17. Observed last spring frost in recent years: 2021 April 25, 2022 April 26, 2023 April 23, 2024 April 21, 2025 May 20, 2026 May 6.Spring: last frostChance of a frost after this date10%50%90%May 1May 14May 2Apr 172021: April 252022: April 262023: April 232024: April 212025: May 202026: May 6Fall near Greeley: chance of a frost before this dateFall, chance of a frost before the date: 10% September 26, 20% October 1, 30% October 3, 40% October 5, 50% October 8, 60% October 11, 70% October 14, 80% October 17, 90% October 21. Observed first fall frost in recent years: 2021 October 16, 2022 October 24, 2023 October 14, 2024 October 25, 2025 October 19.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 26Oct 8Oct 212021: October 162022: October 242023: October 142024: October 252025: 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
2021April 25October 16
2022April 26October 24
2023April 23October 14
2024April 21October 25
2025May 20October 19
2026May 6season not over yet

What these dates mean

Planting tender crops on April 17 in the Greeley area is a gamble; that early spring date carries a 90% chance of a light frost later in the season. The cautious spring date for tender crops is May 14, when only a 10% chance of a light frost remains.

The 50% date is May 2, which means there is a 50% chance of a light frost later than this date. The 50% date is October 8, indicating a 50% chance of a light frost earlier than this date. For a cautious fall schedule, September 26 is the date with only a 10% chance that a light frost has already arrived. The 50% hard-frost dates are April 20 and October 18, and a hard frost at 28°F can damage plants that would survive a 32°F light frost.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after May 14" 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 26" 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 Greeley, CONumbered nearest stations: 1 — Loveland, CO — 20 mi; 2 — Fort Collins 4 E, CO — 21 mi; 3 — Fort Collins, CO — 24 mi; 4 — Brighton, CO — 33 mi; 5 — Northglenn, CO — 39 mi.COWY25 mi · 40 km1. Loveland, CO — 20 mi12. Fort Collins 4 E, CO — 21 mi23. Fort Collins, CO — 24 mi34. Brighton, CO — 33 mi45. Northglenn, CO — 39 mi5
  1. Loveland, CO 20 mi (33 km)
  2. Fort Collins 4 E, CO 21 mi (34 km)
  3. Fort Collins, CO 24 mi (38 km)
  4. Brighton, CO 33 mi (52 km)
  5. Northglenn, CO 39 mi (62 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: 40.4022, -104.6992.