U.S. Frost Dates by Weather Station

NOAA station USC00488852 · Wyoming

Frost Dates for Tensleep 4 NE, WY

NOAA weather station Tensleep 4 NE (USC00488852), Wyoming · elevation 4748 ft (1447 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 1050% chance of a frost after it
  • Typical first fall frostOctober 150% chance of a frost before it
  • Frost-free season141 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Tensleep 4 NE, WYSpring: a frost after April 27 in 9 years out of 10, after May 10 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before October 1 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 141 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 10First frost ~Oct 1Frost season at Tensleep 4 NE, WYSpring: a frost after April 27 in 9 years out of 10, after May 10 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before October 1 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 141 days.JFMAMJJASONDLast frost ~May 10First frost ~Oct 1
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)May 26September 18
50% (typical)May 10October 1
90% (likely)April 27October 16
Frost-free season (32°F, 50% chance)
141 days
Hard frost (28°F), last in spring, 50% chance after
April 29
Hard frost (28°F), first in fall, 50% chance before
October 12

The last 15 years (2006–2020 normals)

Typical last frost May 11 (1 day later than the 30-year normal), typical first fall frost October 4 (3 days later). Frost-free season 144 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 4 NE: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 21, 30% May 17, 40% May 14, 50% May 10, 60% May 8, 70% May 5, 80% May 1, 90% April 27. Observed last spring frost in recent years: 2021 May 22, 2022 May 22, 2023 April 28, 2024 May 8, 2025 May 7, 2026 May 22.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 10Apr 272021: May 222022: May 222023: April 282024: May 82025: May 72026: May 22Fall at Tensleep 4 NE: chance of a frost before this dateFall, chance of a frost before the date: 10% September 18, 20% September 22, 30% September 26, 40% September 29, 50% October 1, 60% October 4, 70% October 7, 80% October 11, 90% October 16. Observed first fall frost in recent years: 2022 October 16, 2023 October 25, 2024 October 19, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 18Oct 1Oct 162022: October 162023: October 252024: 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 22incomplete record
2022May 22October 16
2023April 28October 25
2024May 8October 19
2025May 7October 7
2026May 22season not over yet

What these dates mean

September 18 is the cautious fall date for finishing the harvest in Tensleep 4 NE. In spring the cautious date for setting out tender crops is May 26, which carries only a 10 % chance of a light frost later. The 50% date in spring is May 10, which represents an even chance of a light frost. The 50% date in fall is October 1, which represents an even chance of a light frost. The gamble dates are April 27 in spring (90 % chance later) and October 16 in fall (90 % chance earlier).

Hard frost at 28 °F, marked by the 50% dates April 29 in spring and October 12 in fall, can damage plants more severely than a light frost at 32 °F, so gardeners should allow extra protection when temperatures approach those thresholds.

How to read the probabilities

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

  • Spring: "10% after May 26" 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 18" 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 4 NE, WYNumbered nearest stations: 1 — Tensleep 16 SSE, WY — 18 mi; 2 — Worland (USW00024062), WY — 29 mi; 3 — Worland (USC00489770), WY — 29 mi; 4 — Basin, WY — 39 mi; 5 — Buffalo, WY — 39 mi.25 mi · 40 km1. Tensleep 16 SSE, WY — 18 mi12. Worland (USW00024062), WY — 29 mi23. Worland (USC00489770), WY — 29 mi34. Basin, WY — 39 mi45. Buffalo, WY — 39 mi5
  1. Tensleep 16 SSE, WY 18 mi (28 km)
  2. Worland (USW00024062), WY 29 mi (47 km)
  3. Worland (USC00489770), WY 29 mi (47 km)
  4. Basin, WY 39 mi (63 km)
  5. Buffalo, WY 39 mi (63 km)

Sources

* Hardiness zone 5b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 44.0647, -107.3819.