U.S. Frost Dates by Weather Station

NOAA station USC00488997 · Wyoming

Frost Dates for Torrington, WY

NOAA weather station Torrington 29 N (USC00488997), Wyoming · elevation 4860 ft (1481 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 31only 1 spring in 10 still has a frost later
  • Typical last frostMay 1750% chance of a frost after it
  • Typical first fall frostSeptember 2850% chance of a frost before it
  • Frost-free season133 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Torrington, WYSpring: a frost after May 6 in 9 years out of 10, after May 17 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 28 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 133 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 17First frost ~Sep 28Frost season at Torrington, WYSpring: a frost after May 6 in 9 years out of 10, after May 17 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 28 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 133 days.JFMAMJJASONDLast frost ~May 17First frost ~Sep 28
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)May 31September 15
50% (typical)May 17September 28
90% (likely)May 6October 11
Frost-free season (32°F, 50% chance)
133 days
Hard frost (28°F), last in spring, 50% chance after
May 6
Hard frost (28°F), first in fall, 50% chance before
October 7

The last 15 years (2006–2020 normals)

Typical last frost May 17 (same as the 30-year normal), typical first fall frost October 2 (4 days later). Frost-free season 137 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 Torrington: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 31, 20% May 26, 30% May 23, 40% May 20, 50% May 17, 60% May 14, 70% May 12, 80% May 9, 90% May 6. Observed last spring frost in recent years: 2021 May 13, 2022 May 24, 2023 May 2, 2024 June 19, 2025 May 3, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 31May 17May 62021: May 132022: May 242023: May 22024: June 192025: May 32026: May 19Fall at Torrington: chance of a frost before this dateFall, chance of a frost before the date: 10% September 15, 20% September 20, 30% September 23, 40% September 26, 50% September 28, 60% October 1, 70% October 3, 80% October 6, 90% October 11. Observed first fall frost in recent years: 2021 October 13, 2022 October 17, 2023 October 7, 2024 October 1, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 15Sep 28Oct 112021: October 132022: October 172023: October 72024: October 12025: October 13
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 13October 13
2022May 24October 17
2023May 2October 7
2024June 19October 1
2025May 3October 13
2026May 19season not over yet

What these dates mean

May 31, with a 10 % chance of a light frost later, is the cautious date for setting out tender crops in Torrington. It allows a gardener to plan transplanting seedlings into the garden with minimal risk of frost damage.

The 50 % dates—May 17 in spring and September 28 in fall—represent a 50 % chance of a light frost later than May 17 and a 50 % chance of a light frost earlier than September 28, giving a neutral risk reference. September 15, with a 10 % chance of a light frost earlier, is the cautious date to finish harvesting tender crops before frost arrives. Hard frosts at 28 °F are more damaging than light frosts at 32 °F because they can freeze plant tissue more deeply. The hard-frost 50 % dates are May 6, which carries a 50 % chance of a hard frost later, and October 7, which carries a 50 % chance of a hard frost earlier.

How to read the probabilities

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

  • Spring: "10% after May 31" 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 15" 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 Torrington, WYNumbered nearest stations: 1 — Harrison, NE — 19 mi; 2 — Old Fort Laramie, WY — 28 mi; 3 — Wheatland, WY — 48 mi; 4 — near Scottsbluff, NE — 51 mi; 5 — Redbird, WY — 53 mi.WYNESD25 mi · 40 km1. Harrison, NE — 19 mi12. Old Fort Laramie, WY — 28 mi23. Wheatland, WY — 48 mi34. near Scottsbluff, NE — 51 mi45. Redbird, WY — 53 mi5
  1. Harrison, NE 19 mi (31 km)
  2. Old Fort Laramie, WY 28 mi (45 km)
  3. Wheatland, WY 48 mi (78 km)
  4. near Scottsbluff, NE 51 mi (83 km)
  5. Redbird, WY 53 mi (85 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: 42.4881, -104.1564.