U.S. Frost Dates by Weather Station

NOAA station USC00480484 · Wyoming

Frost Dates for Baggs, WY

NOAA weather station Baggs (USC00480484), Wyoming · elevation 6319 ft (1926 m) · hardiness zone 4b*

  • Lower-risk planting dateafter June 18only 1 spring in 10 still has a frost later
  • Typical last frostJune 150% chance of a frost after it
  • Typical first fall frostSeptember 1850% chance of a frost before it
  • Frost-free season108 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Baggs, WYSpring: a frost after May 15 in 9 years out of 10, after June 1 in half of the years, after June 18 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 October 1 in 9 years out of 10. Typical frost-free season: 108 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Jun 1First frost ~Sep 18Frost season at Baggs, WYSpring: a frost after May 15 in 9 years out of 10, after June 1 in half of the years, after June 18 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 October 1 in 9 years out of 10. Typical frost-free season: 108 days.JFMAMJJASONDLast frost ~Jun 1First 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.

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 18September 4
50% (typical)June 1September 18
90% (likely)May 15October 1
Frost-free season (32°F, 50% chance)
108 days
Hard frost (28°F), last in spring, 50% chance after
May 13
Hard frost (28°F), first in fall, 50% chance before
September 28

The last 15 years (2006–2020 normals)

Typical last frost May 26 (6 days earlier than the 30-year normal), typical first fall frost September 24 (6 days later). Frost-free season 118 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 Baggs: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 18, 20% June 11, 30% June 7, 40% June 4, 50% June 1, 60% May 29, 70% May 25, 80% May 21, 90% May 15. Observed last spring frost in recent years: 2022 June 15, 2024 May 24.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jul 1Jun 18Jun 1May 152022: June 152024: May 24Fall at Baggs: chance of a frost before this dateFall, chance of a frost before the date: 10% September 4, 20% September 9, 30% September 12, 40% September 15, 50% September 18, 60% September 20, 70% September 24, 80% September 27, 90% October 1. Observed first fall frost in recent years: 2025 September 17.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 4Sep 18Oct 12025: September 17
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
2021no dataincomplete record
2022June 15incomplete record
2023incomplete recordincomplete record
2024May 24incomplete record
2025incomplete recordSeptember 17
2026incomplete recordseason not over yet

What these dates mean

The 108 days between the 50% dates in Baggs—June 1 and September 18—mark the period in which a light frost is as likely to have occurred as not, giving gardeners an even-odds window for planning.

For a cautious spring start, the June 18 date carries only a 10 % chance of a light frost later, while the May 15 date carries a 90 % chance and is a gamble. In the fall, the September 4 date has only a 10 % chance of a light frost earlier, whereas October 1 carries a 90 % chance and is a gamble. The 50% hard-frost dates are May 13 in spring and September 28 in fall; a hard frost at 28 °F can damage plant tissue more severely than a light frost at 32 °F. The record spans 26 years.

How to read the probabilities

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

  • Spring: "10% after June 18" 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 Baggs, WYNumbered nearest stations: 1 — Maybell, CO — 43 mi; 2 — Hayden, CO — 43 mi; 3 — Rawlins, WY — 58 mi; 4 — Meeker, CO — 70 mi; 5 — Rock Springs, WY — 82 mi.WYCOUT50 mi · 80 km1. Maybell, CO — 43 mi12. Hayden, CO — 43 mi23. Rawlins, WY — 58 mi34. Meeker, CO — 70 mi45. Rock Springs, WY — 82 mi5
  1. Maybell, CO 43 mi (69 km)
  2. Hayden, CO 43 mi (70 km)
  3. Rawlins, WY 58 mi (93 km)
  4. Meeker, CO 70 mi (113 km)
  5. Rock Springs, WY 82 mi (132 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: 41.0383, -107.6578.