U.S. Frost Dates by Weather Station

NOAA station USW00024137 · Montana

Frost Dates for Cut Bank, MT

NOAA weather station Cut Bank Municipal Airport (USW00024137), Montana · elevation 3838 ft (1170 m) · hardiness zone 4a*

  • Lower-risk planting dateafter June 5only 1 spring in 10 still has a frost later
  • Typical last frostMay 2450% chance of a frost after it
  • Typical first fall frostSeptember 1550% chance of a frost before it
  • Frost-free season113 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Cut Bank, MTSpring: a frost after May 11 in 9 years out of 10, after May 24 in half of the years, after June 5 in 1 year out of 10. Fall: the first frost comes before September 1 in 1 year out of 10, before September 15 in half of the years, before September 27 in 9 years out of 10. Typical frost-free season: 113 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 24First frost ~Sep 15Frost season at Cut Bank, MTSpring: a frost after May 11 in 9 years out of 10, after May 24 in half of the years, after June 5 in 1 year out of 10. Fall: the first frost comes before September 1 in 1 year out of 10, before September 15 in half of the years, before September 27 in 9 years out of 10. Typical frost-free season: 113 days.JFMAMJJASONDLast frost ~May 24First frost ~Sep 15
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 5September 1
50% (typical)May 24September 15
90% (likely)May 11September 27
Frost-free season (32°F, 50% chance)
113 days
Hard frost (28°F), last in spring, 50% chance after
May 11
Hard frost (28°F), first in fall, 50% chance before
September 25

The last 15 years (2006–2020 normals)

Typical last frost May 21 (3 days earlier than the 30-year normal), typical first fall frost September 17 (2 days later). Frost-free season 119 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 Cut Bank: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 5, 20% June 1, 30% May 29, 40% May 26, 50% May 24, 60% May 21, 70% May 18, 80% May 15, 90% May 11. Observed last spring frost in recent years: 2021 May 24, 2022 June 2, 2023 June 21, 2024 June 1, 2025 May 22.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 5May 24May 112021: May 242022: June 22023: June 212024: June 12025: May 22Fall at Cut Bank: chance of a frost before this dateFall, chance of a frost before the date: 10% September 1, 20% September 6, 30% September 10, 40% September 12, 50% September 15, 60% September 17, 70% September 20, 80% September 23, 90% September 27. Observed first fall frost in recent years: 2021 September 16, 2022 September 20, 2023 September 29, 2024 September 21.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 1Sep 15Sep 272021: September 162022: September 202023: September 292024: September 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
2021May 24September 16
2022June 2September 20
2023June 21September 29
2024June 1September 21
2025May 22incomplete record
2026incomplete recordseason not over yet

What these dates mean

The 113 days between the 50% dates in Cut Bank – May 24 and September 15 – define the period where a light frost has a 50 % chance of having occurred in spring and a 50 % chance of not yet arrived in fall. Within this window a gardener can expect an even odds situation for light frost.

For a cautious spring planting the June 5 date is used; it carries only a 10 % chance that a light frost will come later, while the May 11 date represents a 90 % chance and is a gamble. In the fall the September 1 date is the cautious choice, with only a 10 % chance that a light frost has already arrived, whereas September 27 carries a 90 % chance and is risky.

A hard frost at 28 °F is more damaging than a light frost at 32 °F, so the median hard-frost dates of May 11 and September 25 are important reference points.

How to read the probabilities

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

  • Spring: "10% after June 5" 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 1" 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 Cut Bank, MTNumbered nearest stations: 1 — Conrad, MT — 36 mi; 2 — Choteau, MT — 55 mi; 3 — Fairfield, MT — 71 mi; 4 — West Glacier, MT — 74 mi; 5 — Sun River, MT — 83 mi.MT25 mi · 40 km1. Conrad, MT — 36 mi12. Choteau, MT — 55 mi23. Fairfield, MT — 71 mi34. West Glacier, MT — 74 mi45. Sun River, MT — 83 mi5
  1. Conrad, MT 36 mi (57 km)
  2. Choteau, MT 55 mi (88 km)
  3. Fairfield, MT 71 mi (114 km)
  4. West Glacier, MT 74 mi (119 km)
  5. Sun River, MT 83 mi (134 km)

Sources

* Hardiness zone 4a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 48.6033, -112.3753.