U.S. Frost Dates by Weather Station

NOAA station USC00485770 · Wyoming

Frost Dates for Lovell, WY

NOAA weather station Lovell (USC00485770), Wyoming · elevation 3847 ft (1173 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 25only 1 spring in 10 still has a frost later
  • Typical last frostMay 950% chance of a frost after it
  • Typical first fall frostSeptember 2950% chance of a frost before it
  • Frost-free season142 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Lovell, WYSpring: a frost after April 27 in 9 years out of 10, after May 9 in half of the years, after May 25 in 1 year out of 10. Fall: the first frost comes before September 16 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 142 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 9First frost ~Sep 29Frost season at Lovell, WYSpring: a frost after April 27 in 9 years out of 10, after May 9 in half of the years, after May 25 in 1 year out of 10. Fall: the first frost comes before September 16 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 142 days.JFMAMJJASONDLast frost ~May 9First frost ~Sep 29
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 25September 16
50% (typical)May 9September 29
90% (likely)April 27October 11
Frost-free season (32°F, 50% chance)
142 days
Hard frost (28°F), last in spring, 50% chance after
April 29
Hard frost (28°F), first in fall, 50% chance before
October 9

The last 15 years (2006–2020 normals)

Typical last frost May 6 (3 days earlier than the 30-year normal), typical first fall frost October 2 (3 days later). Frost-free season 145 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 Lovell: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 25, 20% May 19, 30% May 15, 40% May 12, 50% May 9, 60% May 6, 70% May 3, 80% April 30, 90% April 27. Observed last spring frost in recent years: 2021 April 24, 2022 May 21, 2023 April 28, 2024 May 4.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 25May 9Apr 272021: April 242022: May 212023: April 282024: May 4Fall at Lovell: chance of a frost before this dateFall, chance of a frost before the date: 10% September 16, 20% September 21, 30% September 24, 40% September 27, 50% September 29, 60% October 1, 70% October 4, 80% October 7, 90% October 11. Observed first fall frost in recent years: 2021 October 1, 2022 October 15, 2023 October 25, 2024 September 22, 2025 October 21.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 16Sep 29Oct 112021: October 12022: October 152023: October 252024: September 222025: October 21
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
2021April 24October 1
2022May 21October 15
2023April 28October 25
2024May 4September 22
2025incomplete recordOctober 21
2026incomplete recordseason not over yet

What these dates mean

May 25 is the cautious spring date; with only a 10 % chance of a light frost after it, a gardener can plan to set out tender crops knowing the risk of frost is low.

The 50 % date is May 9, meaning the odds of a light frost later are even; the 50 % date is September 29, indicating an even chance of a light frost earlier. For a safe finish to tender-crop harvest, the cautious fall date is September 16, when there is just a 10 % chance that a light frost has already arrived. The hard-frost median dates are April 29 in spring and October 9 in fall.

A hard frost at 28 °F can damage or kill plants that survive a light frost at 32 °F, making it a more critical threshold for garden planning.

How to read the probabilities

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

  • Spring: "10% after May 25" 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 16" 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 Lovell, WYNumbered nearest stations: 1 — Deaver, WY — 10 mi; 2 — Powell, WY — 18 mi; 3 — Emblem, WY — 24 mi; 4 — Basin, WY — 36 mi; 5 — Yellowtail Dam, MT — 40 mi.MT25 mi · 40 km1. Deaver, WY — 10 mi12. Powell, WY — 18 mi23. Emblem, WY — 24 mi34. Basin, WY — 36 mi45. Yellowtail Dam, MT — 40 mi5
  1. Deaver, WY 10 mi (16 km)
  2. Powell, WY 18 mi (29 km)
  3. Emblem, WY 24 mi (38 km)
  4. Basin, WY 36 mi (59 km)
  5. Yellowtail Dam, MT 40 mi (64 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: 44.8378, -108.4039.