U.S. Frost Dates by Weather Station

NOAA station USW00024021 · Wyoming

Frost Dates near Lander, WY

NOAA weather station Lander Hunt Field Airport (USW00024021), Wyoming · elevation 5592 ft (1704 m) · hardiness zone 5a*

Lander is the nearest town to the station (1.2 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 June 3only 1 spring in 10 still has a frost later
  • Typical last frostMay 1850% chance of a frost after it
  • Typical first fall frostSeptember 2750% chance of a frost before it
  • Frost-free season131 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season near Lander, WYSpring: a frost after May 4 in 9 years out of 10, after May 18 in half of the years, after June 3 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before September 27 in half of the years, before October 10 in 9 years out of 10. Typical frost-free season: 131 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 18First frost ~Sep 27Frost season near Lander, WYSpring: a frost after May 4 in 9 years out of 10, after May 18 in half of the years, after June 3 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before September 27 in half of the years, before October 10 in 9 years out of 10. Typical frost-free season: 131 days.JFMAMJJASONDLast frost ~May 18First frost ~Sep 27
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 3September 13
50% (typical)May 18September 27
90% (likely)May 4October 10
Frost-free season (32°F, 50% chance)
131 days
Hard frost (28°F), last in spring, 50% chance after
May 4
Hard frost (28°F), first in fall, 50% chance before
October 6

The last 15 years (2006–2020 normals)

Typical last frost May 17 (1 day earlier than the 30-year normal), typical first fall frost October 2 (5 days later). Frost-free season 134 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 Lander: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 3, 20% May 29, 30% May 25, 40% May 21, 50% May 18, 60% May 16, 70% May 12, 80% May 9, 90% May 4. Observed last spring frost in recent years: 2021 May 10, 2022 May 22, 2023 April 28, 2024 May 24, 2025 May 16, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 3May 18May 42021: May 102022: May 222023: April 282024: May 242025: May 162026: May 19Fall near Lander: chance of a frost before this dateFall, chance of a frost before the date: 10% September 13, 20% September 19, 30% September 22, 40% September 25, 50% September 27, 60% September 30, 70% October 2, 80% October 5, 90% October 10. Observed first fall frost in recent years: 2021 September 21, 2022 October 16, 2023 October 14, 2024 October 1, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 13Sep 27Oct 102021: September 212022: October 162023: October 142024: October 12025: 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 10September 21
2022May 22October 16
2023April 28October 14
2024May 24October 1
2025May 16October 7
2026May 19season not over yet

What these dates mean

September 13 is the cautious fall date in the Lander area for finishing the harvest, marking the point at which there is only a 10 % chance that a light frost has already arrived. In spring the cautious date for setting out tender crops is June 3, when a light frost later than that date occurs with only a 10 % chance; planting on May 4 carries a 90 % chance of a frost later and is a gamble. The 50 % dates—May 18 for spring and September 27 for fall—represent the median moment when a light frost is equally likely to have occurred or not, providing a statistical reference point for gardeners.

The hard-frost 50 % dates are May 4 in spring and October 6 in fall; a 28 °F frost can damage plants more severely than a 32 °F light frost because it reaches colder temperatures.

How to read the probabilities

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

  • Spring: "10% after June 3" 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 13" 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 Lander, WYNumbered nearest stations: 1 — Burris, WY — 47 mi; 2 — Jeffrey City, WY — 51 mi; 3 — Thermopolis, WY — 63 mi; 4 — Rock Springs, WY — 86 mi; 5 — Worland (USW00024062), WY — 89 mi.IDUT50 mi · 80 km1. Burris, WY — 47 mi12. Jeffrey City, WY — 51 mi23. Thermopolis, WY — 63 mi34. Rock Springs, WY — 86 mi45. Worland (USW00024062), WY — 89 mi5
  1. Burris, WY 47 mi (76 km)
  2. Jeffrey City, WY 51 mi (82 km)
  3. Thermopolis, WY 63 mi (102 km)
  4. Rock Springs, WY 86 mi (138 km)
  5. Worland (USW00024062), WY 89 mi (142 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: 42.8153, -108.7261.