U.S. Frost Dates by Weather Station

NOAA station USC00481165 · Wyoming

Frost Dates for Buffalo, WY

NOAA weather station Buffalo (USC00481165), Wyoming · elevation 4639 ft (1414 m) · hardiness zone 5a*

  • Lower-risk planting dateafter June 9only 1 spring in 10 still has a frost later
  • Typical last frostMay 2450% chance of a frost after it
  • Typical first fall frostSeptember 2150% chance of a frost before it
  • Frost-free season118 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Buffalo, WYSpring: a frost after May 12 in 9 years out of 10, after May 24 in half of the years, after June 9 in 1 year out of 10. Fall: the first frost comes before September 7 in 1 year out of 10, before September 21 in half of the years, before October 3 in 9 years out of 10. Typical frost-free season: 118 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 24First frost ~Sep 21Frost season at Buffalo, WYSpring: a frost after May 12 in 9 years out of 10, after May 24 in half of the years, after June 9 in 1 year out of 10. Fall: the first frost comes before September 7 in 1 year out of 10, before September 21 in half of the years, before October 3 in 9 years out of 10. Typical frost-free season: 118 days.JFMAMJJASONDLast frost ~May 24First frost ~Sep 21
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 9September 7
50% (typical)May 24September 21
90% (likely)May 12October 3
Frost-free season (32°F, 50% chance)
118 days
Hard frost (28°F), last in spring, 50% chance after
May 12
Hard frost (28°F), first in fall, 50% chance before
September 30

The last 15 years (2006–2020 normals)

Typical last frost May 23 (1 day earlier than the 30-year normal), typical first fall frost September 25 (4 days later). Frost-free season 122 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 Buffalo: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 9, 20% June 3, 30% May 31, 40% May 28, 50% May 24, 60% May 22, 70% May 19, 80% May 16, 90% May 12. Observed last spring frost in recent years: 2023 April 30.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 9May 24May 122023: April 30Fall at Buffalo: chance of a frost before this dateFall, chance of a frost before the date: 10% September 7, 20% September 12, 30% September 15, 40% September 18, 50% September 21, 60% September 23, 70% September 26, 80% September 29, 90% October 3.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 7Sep 21Oct 3
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
2021no datano data
2022no dataincomplete record
2023April 30incomplete record
2024incomplete recordno data
2025no datano data
2026no dataseason not over yet

What these dates mean

Setting out tender crops on the early spring date, May 12, carries a 90 % chance of a frost later than that date, so planting then is a gamble for Buffalo gardeners.

The cautious spring date is June 9, when there is only a 10 % chance of a later frost, and the cautious fall date is September 7, with a 10 % chance of an earlier frost. May 24 is the 50 % date; there is a 50 % chance of a frost later than this date, and September 21 is the 50 % date; there is a 50 % chance of a frost earlier than this date. The interval between the two 32 °F 50 % dates spans 118 days across the 29-year record.

Hard-frost (28 °F) risk is indicated by the 50 % dates May 12 and September 30, and it matters more than a light frost because temperatures that low can cause far greater damage to plant tissue.

How to read the probabilities

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

  • Spring: "10% after June 9" 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 7" 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 Buffalo, WYNumbered nearest stations: 1 — Clearmont, WY — 20 mi; 2 — near Sheridan, WY — 32 mi; 3 — Tensleep 4 NE, WY — 39 mi; 4 — Leiter, WY — 40 mi; 5 — Kaycee, WY — 44 mi.MT25 mi · 40 km1. Clearmont, WY — 20 mi12. near Sheridan, WY — 32 mi23. Tensleep 4 NE, WY — 39 mi34. Leiter, WY — 40 mi45. Kaycee, WY — 44 mi5
  1. Clearmont, WY 20 mi (32 km)
  2. near Sheridan, WY 32 mi (51 km)
  3. Tensleep 4 NE, WY 39 mi (63 km)
  4. Leiter, WY 40 mi (64 km)
  5. Kaycee, WY 44 mi (71 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: 44.3544, -106.6994.