U.S. Frost Dates by Weather Station

NOAA station USW00024018 · Wyoming

Frost Dates for Cheyenne, WY

NOAA weather station Cheyenne (USW00024018), Wyoming · elevation 6128 ft (1868 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 1250% chance of a frost after it
  • Typical first fall frostOctober 150% chance of a frost before it
  • Frost-free season141 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Cheyenne, WYSpring: a frost after May 1 in 9 years out of 10, after May 12 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 18 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: 141 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 12First frost ~Oct 1Frost season at Cheyenne, WYSpring: a frost after May 1 in 9 years out of 10, after May 12 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 18 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: 141 days.JFMAMJJASONDLast frost ~May 12First 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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 26September 18
50% (typical)May 12October 1
90% (likely)May 1October 14
Frost-free season (32°F, 50% chance)
141 days
Hard frost (28°F), last in spring, 50% chance after
May 2
Hard frost (28°F), first in fall, 50% chance before
October 11

The last 15 years (2006–2020 normals)

Typical last frost May 14 (2 days later than the 30-year normal), typical first fall frost October 5 (4 days later). Frost-free season 144 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 Cheyenne: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 21, 30% May 18, 40% May 15, 50% May 12, 60% May 10, 70% May 8, 80% May 5, 90% May 1. Observed last spring frost in recent years: 2021 May 11, 2022 May 22, 2023 April 28, 2024 May 11, 2025 May 2, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 12May 12021: May 112022: May 222023: April 282024: May 112025: May 22026: May 19Fall at Cheyenne: chance of a frost before this dateFall, chance of a frost before the date: 10% September 18, 20% September 24, 30% September 27, 40% September 30, 50% October 1, 60% October 4, 70% October 7, 80% October 10, 90% October 14. Observed first fall frost in recent years: 2021 October 12, 2022 October 8, 2023 October 7, 2024 October 25, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 18Oct 1Oct 142021: October 122022: October 82023: October 72024: October 252025: October 13
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 11October 12
2022May 22October 8
2023April 28October 7
2024May 11October 25
2025May 2October 13
2026May 19season not over yet

What these dates mean

The 141 days between the 50% dates in Cheyenne frame the period when light frosts are less likely to interrupt garden work. The 50% spring date is May 12 and the 50% fall date is October 1; on each of those days a gardener faces even odds of a frost later (spring) or earlier (fall). The hard-frost 50% dates are May 2 in spring and October 11 in fall, marking the midpoint of the chance for temperatures to reach 28 °F.

For a cautious plan, the spring date with only a 10 % chance of a later light frost is May 26, used as the latest time to set out tender crops. In the fall, the cautious date with a 10 % chance of an earlier light frost is September 18, when tender crops should be finished harvesting.

A hard frost at 28 °F can damage plants that survive a light frost at 32 °F, so the 28 °F dates are a more critical threshold.

How to read the probabilities

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

  • Spring: "10% after May 26" 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 18" 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 Cheyenne, WYNumbered nearest stations: 1 — Fort Collins 4 E, CO — 41 mi; 2 — Chugwater, WY — 42 mi; 3 — Fort Collins, CO — 42 mi; 4 — Laramie, WY — 46 mi; 5 — New Raymer, CO — 51 mi.WYCONE25 mi · 40 km1. Fort Collins 4 E, CO — 41 mi12. Chugwater, WY — 42 mi23. Fort Collins, CO — 42 mi34. Laramie, WY — 46 mi45. New Raymer, CO — 51 mi5
  1. Fort Collins 4 E, CO 41 mi (67 km)
  2. Chugwater, WY 42 mi (68 km)
  3. Fort Collins, CO 42 mi (68 km)
  4. Laramie, WY 46 mi (75 km)
  5. New Raymer, CO 51 mi (82 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: 41.1519, -104.8061.