U.S. Frost Dates by Weather Station

NOAA station USC00489615 · Wyoming

Frost Dates for Wheatland, WY

NOAA weather station Wheatland 4 N (USC00489615), Wyoming · elevation 4638 ft (1414 m) · hardiness zone 5a*

  • Lower-risk planting dateafter June 2only 1 spring in 10 still has a frost later
  • Typical last frostMay 1950% chance of a frost after it
  • Typical first fall frostSeptember 2250% chance of a frost before it
  • Frost-free season125 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Wheatland, WYSpring: a frost after May 7 in 9 years out of 10, after May 19 in half of the years, after June 2 in 1 year out of 10. Fall: the first frost comes before September 8 in 1 year out of 10, before September 22 in half of the years, before October 4 in 9 years out of 10. Typical frost-free season: 125 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 19First frost ~Sep 22Frost season at Wheatland, WYSpring: a frost after May 7 in 9 years out of 10, after May 19 in half of the years, after June 2 in 1 year out of 10. Fall: the first frost comes before September 8 in 1 year out of 10, before September 22 in half of the years, before October 4 in 9 years out of 10. Typical frost-free season: 125 days.JFMAMJJASONDLast frost ~May 19First frost ~Sep 22
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 2September 8
50% (typical)May 19September 22
90% (likely)May 7October 4
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 1

The last 15 years (2006–2020 normals)

Typical last frost May 11 (8 days earlier than the 30-year normal), typical first fall frost October 2 (10 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 Wheatland: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 2, 20% May 28, 30% May 24, 40% May 22, 50% May 19, 60% May 16, 70% May 14, 80% May 10, 90% May 7. Observed last spring frost in recent years: 2021 May 12, 2022 May 22.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 2May 19May 72021: May 122022: May 22Fall at Wheatland: chance of a frost before this dateFall, chance of a frost before the date: 10% September 8, 20% September 13, 30% September 16, 40% September 19, 50% September 22, 60% September 25, 70% September 28, 80% October 1, 90% October 4. Observed first fall frost in recent years: 2021 September 30, 2022 October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 8Sep 22Oct 42021: September 302022: October 8
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 12September 30
2022May 22October 8
2023incomplete recordno data
2024no datano data
2025no datano data
2026no dataseason not over yet

What these dates mean

The 125 days between the 32°F 50% dates, May 19 and September 22, frame the window in which gardeners can grow tender crops without a light frost. The 50% date marks the point at which there is an even (50 %) chance of a light frost occurring later in spring or earlier in fall.

For a cautious planting schedule, the spring LATE date of June 2 is used to set out tender crops, while the fall EARLY date of September 8 signals when to finish harvesting them. The hard-frost median dates, May 9 in spring and October 1 in fall, show when a 28°F frost becomes a 50 % possibility; a hard frost at 28°F can damage plants that survive a light frost at 32°F. Planting as early as May 7 in spring or as late as October 4 in fall carries a 90 % chance of encountering a light frost and is therefore a gamble. These percentages reflect 26 years of NOAA climate normals (1991-2020).

How to read the probabilities

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

  • Spring: "10% after June 2" 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 8" 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 Wheatland, WYNumbered nearest stations: 1 — Old Fort Laramie, WY — 21 mi; 2 — Chugwater, WY — 25 mi; 3 — Torrington, WY — 48 mi; 4 — Harrisburg, NE — 61 mi; 5 — Cheyenne, WY — 67 mi.WYNECO25 mi · 40 km1. Old Fort Laramie, WY — 21 mi12. Chugwater, WY — 25 mi23. Torrington, WY — 48 mi34. Harrisburg, NE — 61 mi45. Cheyenne, WY — 67 mi5
  1. Old Fort Laramie, WY 21 mi (34 km)
  2. Chugwater, WY 25 mi (40 km)
  3. Torrington, WY 48 mi (78 km)
  4. Harrisburg, NE 61 mi (98 km)
  5. Cheyenne, WY 67 mi (107 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: 42.1106, -104.9492.