U.S. Frost Dates by Weather Station

NOAA station USC00480552 · Wyoming

Frost Dates for Bates Creek #2, WY

NOAA weather station Bates Creek #2 (USC00480552), Wyoming · elevation 6042 ft (1842 m) · hardiness zone 5a*

  • Lower-risk planting dateafter June 6only 1 spring in 10 still has a frost later
  • Typical last frostMay 2250% chance of a frost after it
  • Typical first fall frostSeptember 2650% chance of a frost before it
  • Frost-free season125 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Bates Creek #2, WYSpring: a frost after May 8 in 9 years out of 10, after May 22 in half of the years, after June 6 in 1 year out of 10. Fall: the first frost comes before September 11 in 1 year out of 10, before September 26 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 125 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 22First frost ~Sep 26Frost season at Bates Creek #2, WYSpring: a frost after May 8 in 9 years out of 10, after May 22 in half of the years, after June 6 in 1 year out of 10. Fall: the first frost comes before September 11 in 1 year out of 10, before September 26 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 125 days.JFMAMJJASONDLast frost ~May 22First frost ~Sep 26
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 6September 11
50% (typical)May 22September 26
90% (likely)May 8October 9
Frost-free season (32°F, 50% chance)
125 days
Hard frost (28°F), last in spring, 50% chance after
May 9
Hard frost (28°F), first in fall, 50% chance before
October 5

The last 15 years (2006–2020 normals)

Typical last frost May 23 (1 day later than the 30-year normal), typical first fall frost September 29 (3 days later). Frost-free season 125 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 Bates Creek #2: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 6, 20% May 31, 30% May 28, 40% May 25, 50% May 22, 60% May 20, 70% May 17, 80% May 13, 90% May 8. Observed last spring frost in recent years: 2021 May 10, 2022 June 21, 2023 April 29, 2024 May 25, 2025 May 3, 2026 June 12.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 6May 22May 82021: May 102022: June 212023: April 292024: May 252025: May 32026: June 12Fall at Bates Creek #2: chance of a frost before this dateFall, chance of a frost before the date: 10% September 11, 20% September 17, 30% September 21, 40% September 24, 50% September 26, 60% September 29, 70% October 1, 80% October 4, 90% October 9. Observed first fall frost in recent years: 2021 September 21, 2022 September 10, 2023 October 13, 2024 October 19, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 11Sep 26Oct 92021: September 212022: September 102023: October 132024: 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 10September 21
2022June 21September 10
2023April 29October 13
2024May 25October 19
2025May 3October 7
2026June 12season not over yet

What these dates mean

Setting out tender crops on the early spring date, May 8, carries a 90% chance of a light frost later than that day, so it is a gamble for growers at Bates Creek #2. In the autumn, waiting until October 9 to keep tender crops in the garden also involves a 90% chance of a light frost earlier than that date, making the late-season choice equally risky.

The 50% dates—May 22 in spring and September 26 in fall—represent the point at which a light frost is as likely as not; they are not frost dates but give a neutral benchmark for planning. A cautious approach uses the June 6 date, which has only a 10% chance of a later frost, for planting tender crops in spring, and the September 11 date, also with a 10% chance of an earlier frost, for finishing harvests in fall.

Hard frost at 28°F, marked by the May 9 and October 5 median dates, matters more than light frost at 32°F because the lower temperature can cause greater damage to plant tissues.

How to read the probabilities

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

  • Spring: "10% after June 6" 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 11" 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 Bates Creek #2, WYNumbered nearest stations: 1 — Casper, WY — 20 mi; 2 — Midwest, WY — 55 mi; 3 — Rawlins, WY — 71 mi; 4 — Jeffrey City, WY — 75 mi; 5 — Kaycee, WY — 77 mi.WY50 mi · 80 km1. Casper, WY — 20 mi12. Midwest, WY — 55 mi23. Rawlins, WY — 71 mi34. Jeffrey City, WY — 75 mi45. Kaycee, WY — 77 mi5
  1. Casper, WY 20 mi (32 km)
  2. Midwest, WY 55 mi (88 km)
  3. Rawlins, WY 71 mi (114 km)
  4. Jeffrey City, WY 75 mi (121 km)
  5. Kaycee, WY 77 mi (123 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: 42.6233, -106.3567.