U.S. Frost Dates by Weather Station

NOAA station USC00245153 · Montana

Frost Dates for Loma, MT

NOAA weather station Loma (USC00245153), Montana · elevation 2578 ft (786 m) · hardiness zone 3b*

  • Lower-risk planting dateafter June 3only 1 spring in 10 still has a frost later
  • Typical last frostMay 2050% chance of a frost after it
  • Typical first fall frostSeptember 1950% chance of a frost before it
  • Frost-free season120 daystypical year, 32°F
  • Hardiness zone3bcalculated*

The year at a glance

Frost season at Loma, MTSpring: a frost after May 8 in 9 years out of 10, after May 20 in half of the years, after June 3 in 1 year out of 10. Fall: the first frost comes before September 4 in 1 year out of 10, before September 19 in half of the years, before October 2 in 9 years out of 10. Typical frost-free season: 120 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 20First frost ~Sep 19Frost season at Loma, MTSpring: a frost after May 8 in 9 years out of 10, after May 20 in half of the years, after June 3 in 1 year out of 10. Fall: the first frost comes before September 4 in 1 year out of 10, before September 19 in half of the years, before October 2 in 9 years out of 10. Typical frost-free season: 120 days.JFMAMJJASONDLast frost ~May 20First frost ~Sep 19
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 3September 4
50% (typical)May 20September 19
90% (likely)May 8October 2
Frost-free season (32°F, 50% chance)
120 days
Hard frost (28°F), last in spring, 50% chance after
May 9
Hard frost (28°F), first in fall, 50% chance before
September 29

The last 15 years (2006–2020 normals)

Typical last frost May 17 (3 days earlier than the 30-year normal), typical first fall frost September 21 (2 days later). Frost-free season 125 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 Loma: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 3, 20% May 29, 30% May 26, 40% May 23, 50% May 20, 60% May 18, 70% May 15, 80% May 12, 90% May 8. Observed last spring frost in recent years: 2021 May 23, 2022 May 23, 2023 April 29.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 3May 20May 82021: May 232022: May 232023: April 29Fall at Loma: chance of a frost before this dateFall, chance of a frost before the date: 10% September 4, 20% September 9, 30% September 13, 40% September 16, 50% September 19, 60% September 21, 70% September 24, 80% September 27, 90% October 2. Observed first fall frost in recent years: 2021 September 17, 2022 September 21, 2023 October 6, 2024 October 2, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 4Sep 19Oct 22021: September 172022: September 212023: October 62024: October 22025: October 6
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 23September 17
2022May 23September 21
2023April 29October 6
2024incomplete recordOctober 2
2025incomplete recordOctober 6
2026no dataseason not over yet

What these dates mean

June 3 is the cautious spring date for Loma, Montana, with only a 10 % chance of a light frost later; it lets a gardener plan to set out tender crops with low risk. The median light-frost date in spring is May 20, which marks the point where a light frost is equally likely to occur before or after that day. The 50 % hard-frost date in spring is May 9, indicating an even chance of a 28 °F frost around that time.

In fall, September 4 serves as the cautious date, carrying only a 10 % chance that a light frost has arrived earlier, so it marks a window to finish harvesting tender crops. The median light-frost date for autumn is September 19, and the 50 % hard-frost date is September 29. A hard frost matters more because temperatures at 28 °F can damage plant tissue that survives a light frost at 32 °F. The record spans 29 years, giving confidence in these probabilities.

How to read the probabilities

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

  • Spring: "10% after June 3" 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 Loma, MTNumbered nearest stations: 1 — Gildford, MT — 44 mi; 2 — Fort Assiniboine, MT — 50 mi; 3 — Great Falls, MT — 52 mi; 4 — Havre, MT — 54 mi; 5 — Stanford, MT — 56 mi.25 mi · 40 km1. Gildford, MT — 44 mi12. Fort Assiniboine, MT — 50 mi23. Great Falls, MT — 52 mi34. Havre, MT — 54 mi45. Stanford, MT — 56 mi5
  1. Gildford, MT 44 mi (71 km)
  2. Fort Assiniboine, MT 50 mi (81 km)
  3. Great Falls, MT 52 mi (84 km)
  4. Havre, MT 54 mi (87 km)
  5. Stanford, MT 56 mi (89 km)

Sources

* Hardiness zone 3b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 47.9364, -110.5025.