U.S. Frost Dates by Weather Station

NOAA station USW00024022 · Wyoming

Frost Dates for Laramie, WY

NOAA weather station Laramie Regional Airport (USW00024022), Wyoming · elevation 7266 ft (2215 m) · hardiness zone 4b*

  • Lower-risk planting dateafter June 18only 1 spring in 10 still has a frost later
  • Typical last frostJune 250% chance of a frost after it
  • Typical first fall frostSeptember 1550% chance of a frost before it
  • Frost-free season102 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Laramie, WYSpring: a frost after May 21 in 9 years out of 10, after June 2 in half of the years, after June 18 in 1 year out of 10. Fall: the first frost comes before September 3 in 1 year out of 10, before September 15 in half of the years, before September 27 in 9 years out of 10. Typical frost-free season: 102 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Jun 2First frost ~Sep 15Frost season at Laramie, WYSpring: a frost after May 21 in 9 years out of 10, after June 2 in half of the years, after June 18 in 1 year out of 10. Fall: the first frost comes before September 3 in 1 year out of 10, before September 15 in half of the years, before September 27 in 9 years out of 10. Typical frost-free season: 102 days.JFMAMJJASONDLast frost ~Jun 2First frost ~Sep 15
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 18September 3
50% (typical)June 2September 15
90% (likely)May 21September 27
Frost-free season (32°F, 50% chance)
102 days
Hard frost (28°F), last in spring, 50% chance after
May 20
Hard frost (28°F), first in fall, 50% chance before
September 24

The last 15 years (2006–2020 normals)

Typical last frost June 2 (same as the 30-year normal), typical first fall frost September 16 (1 day later). Frost-free season 105 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 Laramie: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 18, 20% June 11, 30% June 8, 40% June 5, 50% June 2, 60% May 31, 70% May 29, 80% May 25, 90% May 21. Observed last spring frost in recent years: 2021 May 27, 2022 June 2, 2023 May 9, 2024 May 24, 2025 May 16, 2026 May 23.Spring: last frostChance of a frost after this date10%50%90%Jun 1Jul 1Jun 18Jun 2May 212021: May 272022: June 22023: May 92024: May 242025: May 162026: May 23Fall at Laramie: chance of a frost before this dateFall, chance of a frost before the date: 10% September 3, 20% September 7, 30% September 10, 40% September 12, 50% September 15, 60% September 18, 70% September 21, 80% September 23, 90% September 27. Observed first fall frost in recent years: 2021 September 20, 2022 September 11, 2023 September 24, 2024 October 19, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 3Sep 15Sep 272021: September 202022: September 112023: September 242024: October 192025: October 7
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 27September 20
2022June 2September 11
2023May 9September 24
2024May 24October 19
2025May 16October 7
2026May 23season not over yet

What these dates mean

Setting out tender crops on the early spring date, May 21, carries a 90 % chance of a light frost and therefore is a gamble in Laramie. For a more cautious approach, the 10 % chance date of June 18 is used to start tender crops, while the counterpart cautious date in fall is September 3 to finish harvesting them.

The 50% date is June 2, indicating a 50 % chance of a light frost later than this date, and the 50% date is September 15, indicating a 50 % chance of a light frost earlier than this date. The median hard-frost dates are May 20 in spring and September 24 in fall; these mark the point where a 28 °F frost is equally likely to have occurred or not.

Because a hard frost at 28 °F can damage plant tissue that survives a 32 °F light frost, it matters more to gardeners.

How to read the probabilities

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

  • Spring: "10% after June 18" 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 3" 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 Laramie, WYNumbered nearest stations: 1 — Rustic, CO — 42 mi; 2 — Cheyenne, WY — 46 mi; 3 — Chugwater, WY — 54 mi; 4 — Fort Collins, CO — 59 mi; 5 — Fort Collins 4 E, CO — 61 mi.WYNE25 mi · 40 km1. Rustic, CO — 42 mi12. Cheyenne, WY — 46 mi23. Chugwater, WY — 54 mi34. Fort Collins, CO — 59 mi45. Fort Collins 4 E, CO — 61 mi5
  1. Rustic, CO 42 mi (68 km)
  2. Cheyenne, WY 46 mi (75 km)
  3. Chugwater, WY 54 mi (87 km)
  4. Fort Collins, CO 59 mi (96 km)
  5. Fort Collins 4 E, CO 61 mi (98 km)

Sources

* Hardiness zone 4b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 41.3119, -105.6747.