U.S. Frost Dates by Weather Station

NOAA station USC00481816 · Wyoming

Frost Dates for Clearmont, WY

NOAA weather station Clearmont 5 SW (USC00481816), Wyoming · elevation 3995 ft (1218 m) · hardiness zone 4b*

  • Lower-risk planting dateafter June 8only 1 spring in 10 still has a frost later
  • Typical last frostMay 2450% chance of a frost after it
  • Typical first fall frostSeptember 1650% chance of a frost before it
  • Frost-free season114 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Clearmont, WYSpring: a frost after May 12 in 9 years out of 10, after May 24 in half of the years, after June 8 in 1 year out of 10. Fall: the first frost comes before September 3 in 1 year out of 10, before September 16 in half of the years, before October 1 in 9 years out of 10. Typical frost-free season: 114 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 24First frost ~Sep 16Frost season at Clearmont, WYSpring: a frost after May 12 in 9 years out of 10, after May 24 in half of the years, after June 8 in 1 year out of 10. Fall: the first frost comes before September 3 in 1 year out of 10, before September 16 in half of the years, before October 1 in 9 years out of 10. Typical frost-free season: 114 days.JFMAMJJASONDLast frost ~May 24First frost ~Sep 16
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 8September 3
50% (typical)May 24September 16
90% (likely)May 12October 1
Frost-free season (32°F, 50% chance)
114 days
Hard frost (28°F), last in spring, 50% chance after
May 10
Hard frost (28°F), first in fall, 50% chance before
September 27

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 18 (2 days later). Frost-free season 115 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 Clearmont: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 8, 20% June 3, 30% May 30, 40% May 27, 50% May 24, 60% May 21, 70% May 19, 80% May 16, 90% May 12. Observed last spring frost in recent years: 2021 May 24, 2022 June 1, 2023 April 30, 2024 June 19, 2025 May 3.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 8May 24May 122021: May 242022: June 12023: April 302024: June 192025: May 3Fall at Clearmont: chance of a frost before this dateFall, chance of a frost before the date: 10% September 3, 20% September 7, 30% September 11, 40% September 14, 50% September 16, 60% September 19, 70% September 22, 80% September 26, 90% October 1. Observed first fall frost in recent years: 2021 September 17, 2022 October 8, 2023 October 6, 2024 September 22, 2025 September 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 3Sep 16Oct 12021: September 172022: October 82023: October 62024: September 222025: September 6
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 24September 17
2022June 1October 8
2023April 30October 6
2024June 19September 22
2025May 3September 6
2026no dataseason not over yet

What these dates mean

September 3 marks the cautious fall date for finishing the harvest of tender crops in Clearmont, where there is only a 10 % chance that a light frost has arrived earlier. The 50% fall date is September 16, a 50 % chance of a light frost earlier than this date, while October 1 carries a 90 % chance and is a gamble for late tender crops.

In spring, the cautious date for setting out tender crops is June 8, when a light frost later than that day occurs only 10 % of the time; May 12, with a 90 % chance, would be a gamble. The 50% spring date is May 24, a 50 % chance of a light frost later than this date. The 50% hard-frost dates are May 10 and September 27; a hard frost at 28 °F can damage plants that survive a 32 °F light frost, making it a greater concern.

How to read the probabilities

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

  • Spring: "10% after June 8" 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 Clearmont, WYNumbered nearest stations: 1 — Buffalo, WY — 20 mi; 2 — Leiter, WY — 20 mi; 3 — near Sheridan, WY — 29 mi; 4 — Moorhead, MT — 54 mi; 5 — Biddle, MT — 57 mi.WYMT25 mi · 40 km1. Buffalo, WY — 20 mi12. Leiter, WY — 20 mi23. near Sheridan, WY — 29 mi34. Moorhead, MT — 54 mi45. Biddle, MT — 57 mi5
  1. Buffalo, WY 20 mi (32 km)
  2. Leiter, WY 20 mi (33 km)
  3. near Sheridan, WY 29 mi (46 km)
  4. Moorhead, MT 54 mi (86 km)
  5. Biddle, MT 57 mi (92 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: 44.5781, -106.4472.