U.S. Frost Dates by Weather Station

NOAA station USC00488858 · Wyoming

Frost Dates for Tensleep 16 SSE, WY

NOAA weather station Tensleep 16 SSE (USC00488858), Wyoming · elevation 4680 ft (1427 m) · hardiness zone 4a*

  • Lower-risk planting dateafter June 7only 1 spring in 10 still has a frost later
  • Typical last frostMay 2250% chance of a frost after it
  • Typical first fall frostSeptember 1850% chance of a frost before it
  • Frost-free season117 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Tensleep 16 SSE, WYSpring: a frost after May 10 in 9 years out of 10, after May 22 in half of the years, after June 7 in 1 year out of 10. Fall: the first frost comes before September 4 in 1 year out of 10, before September 18 in half of the years, before September 30 in 9 years out of 10. Typical frost-free season: 117 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 22First frost ~Sep 18Frost season at Tensleep 16 SSE, WYSpring: a frost after May 10 in 9 years out of 10, after May 22 in half of the years, after June 7 in 1 year out of 10. Fall: the first frost comes before September 4 in 1 year out of 10, before September 18 in half of the years, before September 30 in 9 years out of 10. Typical frost-free season: 117 days.JFMAMJJASONDLast frost ~May 22First frost ~Sep 18
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.Today

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 7September 4
50% (typical)May 22September 18
90% (likely)May 10September 30
Frost-free season (32°F, 50% chance)
117 days
Hard frost (28°F), last in spring, 50% chance after
May 9
Hard frost (28°F), first in fall, 50% chance before
September 28

The last 15 years (2006–2020 normals)

Typical last frost May 22 (same as the 30-year normal), typical first fall frost September 17 (1 day earlier). Frost-free season 116 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 Tensleep 16 SSE: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 7, 20% June 2, 30% May 29, 40% May 25, 50% May 22, 60% May 20, 70% May 17, 80% May 14, 90% May 10. Observed last spring frost in recent years: 2021 May 24, 2022 June 15, 2023 May 10, 2025 June 18, 2026 June 14.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 7May 22May 102021: May 242022: June 152023: May 102025: June 182026: June 14Fall at Tensleep 16 SSE: chance of a frost before this dateFall, chance of a frost before the date: 10% September 4, 20% September 8, 30% September 12, 40% September 15, 50% September 18, 60% September 20, 70% September 23, 80% September 26, 90% September 30. Observed first fall frost in recent years: 2021 September 17, 2022 September 11, 2023 September 24, 2024 September 13, 2025 September 5.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 4Sep 18Sep 302021: September 172022: September 112023: September 242024: September 132025: September 5
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 15September 11
2023May 10September 24
2024incomplete recordSeptember 13
2025June 18September 5
2026June 14season not over yet

What these dates mean

June 7 is the cautious spring date, carrying only a ten-percent chance that a light frost will occur later; it allows a gardener to set out tender crops without imposing a high frost risk. The median light-frost dates are May 22 and September 18; at those points there is a fifty-percent chance of a frost later in spring and earlier in fall. For a conservative schedule the fall cautious date is September 4, when only ten percent of years see a light frost earlier, marking an appropriate moment to finish harvesting tender crops. The hard-frost median dates are May 9 and September 28, and a hard frost at 28 °F can damage plants more severely than a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after June 7" 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 4" 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 Tensleep 16 SSE, WYNumbered nearest stations: 1 — Tensleep 4 NE, WY — 18 mi; 2 — Worland (USW00024062), WY — 31 mi; 3 — Worland (USC00489770), WY — 33 mi; 4 — Kaycee, WY — 37 mi; 5 — Thermopolis, WY — 43 mi.25 mi · 40 km1. Tensleep 4 NE, WY — 18 mi12. Worland (USW00024062), WY — 31 mi23. Worland (USC00489770), WY — 33 mi34. Kaycee, WY — 37 mi45. Thermopolis, WY — 43 mi5
  1. Tensleep 4 NE, WY 18 mi (28 km)
  2. Worland (USW00024062), WY 31 mi (50 km)
  3. Worland (USC00489770), WY 33 mi (53 km)
  4. Kaycee, WY 37 mi (59 km)
  5. Thermopolis, WY 43 mi (70 km)

Sources

* Hardiness zone 4a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 43.8111, -107.3653.