U.S. Frost Dates by Weather Station

NOAA station USW00024057 · Wyoming

Frost Dates for Rawlins, WY

NOAA weather station Rawlins Municipal Airport (USW00024057), Wyoming · elevation 6736 ft (2053 m) · hardiness zone 5a*

  • Lower-risk planting dateafter June 17only 1 spring in 10 still has a frost later
  • Typical last frostJune 150% chance of a frost after it
  • Typical first fall frostSeptember 1550% chance of a frost before it
  • Frost-free season105 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Rawlins, WYSpring: a frost after May 17 in 9 years out of 10, after June 1 in half of the years, after June 17 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 29 in 9 years out of 10. Typical frost-free season: 105 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Jun 1First frost ~Sep 15Frost season at Rawlins, WYSpring: a frost after May 17 in 9 years out of 10, after June 1 in half of the years, after June 17 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 29 in 9 years out of 10. Typical frost-free season: 105 days.JFMAMJJASONDLast frost ~Jun 1First 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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 17September 3
50% (typical)June 1September 15
90% (likely)May 17September 29
Frost-free season (32°F, 50% chance)
105 days
Hard frost (28°F), last in spring, 50% chance after
May 17
Hard frost (28°F), first in fall, 50% chance before
September 26

The last 15 years (2006–2020 normals)

Typical last frost May 30 (2 days earlier than the 30-year normal), typical first fall frost September 18 (3 days later). Frost-free season 110 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 Rawlins: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 17, 20% June 11, 30% June 7, 40% June 4, 50% June 1, 60% May 29, 70% May 25, 80% May 22, 90% May 17. Observed last spring frost in recent years: 2021 May 27, 2022 May 25, 2023 May 8, 2024 May 31, 2025 May 22, 2026 May 22.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jul 1Jun 17Jun 1May 172021: May 272022: May 252023: May 82024: May 312025: May 222026: May 22Fall at Rawlins: 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 13, 50% September 15, 60% September 18, 70% September 21, 80% September 25, 90% September 29. Observed first fall frost in recent years: 2021 September 20, 2022 September 11, 2023 September 25, 2024 September 14, 2025 September 18.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 3Sep 15Sep 292021: September 202022: September 112023: September 252024: September 142025: September 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
2021May 27September 20
2022May 25September 11
2023May 8September 25
2024May 31September 14
2025May 22September 18
2026May 22season not over yet

What these dates mean

June 17 marks the cautious spring light-frost date in Rawlins; with only a 10 % chance of a frost later than that day, a gardener can schedule the first planting of tender crops after it. The 50 % light-frost dates are June 1 in spring and September 15 in fall, meaning there is an even chance of a frost on each of those days. The 28 °F hard-frost median dates are May 17 for spring and September 26 for fall; they are not frost-dates but indicate when hard frosts are equally likely to have occurred.

For the autumn season, September 3 is the cautious light-frost date, with only a 10 % chance that a frost has already arrived, so it guides the latest time to finish harvesting tender crops. A hard frost can damage plants more severely than a light frost because the lower temperature can kill tissue that survives a 32 °F chill.

How to read the probabilities

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

  • Spring: "10% after June 17" 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 Rawlins, WYNumbered nearest stations: 1 — Jeffrey City, WY — 57 mi; 2 — Baggs, WY — 58 mi; 3 — Bates Creek #2, WY — 71 mi; 4 — Casper, WY — 84 mi; 5 — Laramie, WY — 86 mi.WYCO50 mi · 80 km1. Jeffrey City, WY — 57 mi12. Baggs, WY — 58 mi23. Bates Creek #2, WY — 71 mi34. Casper, WY — 84 mi45. Laramie, WY — 86 mi5
  1. Jeffrey City, WY 57 mi (92 km)
  2. Baggs, WY 58 mi (93 km)
  3. Bates Creek #2, WY 71 mi (114 km)
  4. Casper, WY 84 mi (136 km)
  5. Laramie, WY 86 mi (138 km)

Sources

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

Station coordinates: 41.8056, -107.1997.