U.S. Frost Dates by Weather Station

NOAA station USC00241938 · Montana

Frost Dates for Columbus, MT

NOAA weather station Columbus (USC00241938), Montana · elevation 3602 ft (1098 m) · hardiness zone 4b*

  • Lower-risk planting dateafter June 12only 1 spring in 10 still has a frost later
  • Typical last frostMay 2750% chance of a frost after it
  • Typical first fall frostSeptember 1450% chance of a frost before it
  • Frost-free season108 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Columbus, MTSpring: a frost after May 14 in 9 years out of 10, after May 27 in half of the years, after June 12 in 1 year out of 10. Fall: the first frost comes before September 1 in 1 year out of 10, before September 14 in half of the years, before September 28 in 9 years out of 10. Typical frost-free season: 108 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 27First frost ~Sep 14Frost season at Columbus, MTSpring: a frost after May 14 in 9 years out of 10, after May 27 in half of the years, after June 12 in 1 year out of 10. Fall: the first frost comes before September 1 in 1 year out of 10, before September 14 in half of the years, before September 28 in 9 years out of 10. Typical frost-free season: 108 days.JFMAMJJASONDLast frost ~May 27First frost ~Sep 14
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.Today

Frost dates (32°F)

Probability of frost, based on 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 12September 1
50% (typical)May 27September 14
90% (likely)May 14September 28
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 26

The last 15 years (2006–2020 normals)

Typical last frost May 24 (3 days earlier than the 30-year normal), typical first fall frost September 14. Frost-free season 113 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 Columbus: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 12, 20% June 5, 30% June 1, 40% May 30, 50% May 27, 60% May 25, 70% May 22, 80% May 18, 90% May 14. Observed last spring frost in recent years: 2021 May 30, 2022 May 25, 2023 May 10, 2024 June 19, 2025 May 2.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 12May 27May 142021: May 302022: May 252023: May 102024: June 192025: May 2Fall at Columbus: chance of a frost before this dateFall, chance of a frost before the date: 10% September 1, 20% September 5, 30% September 8, 40% September 11, 50% September 14, 60% September 17, 70% September 20, 80% September 23, 90% September 28. Observed first fall frost in recent years: 2021 September 17, 2022 October 13, 2023 October 7, 2024 September 22, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 1Sep 14Sep 282021: September 172022: October 132023: October 72024: September 222025: October 7
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 30September 17
2022May 25October 13
2023May 10October 7
2024June 19September 22
2025May 2October 7
2026incomplete recordseason not over yet

What these dates mean

September 1 marks the cautious fall date for finishing the harvest of tender crops in Columbus, as there is only a 10 % chance that a light frost has arrived earlier.

In the spring, the cautious date for setting out tender crops is June 12, which carries a 10 % chance of a later frost, while the risky early option is May 14 with a 90 % chance. May 27 is the 50 % date for light frost in spring, indicating an even odds point, and September 14 serves the same role for fall.

For hard frost (28 °F), the median dates are May 13 in spring and September 26 in fall; a hard frost can damage plant tissue that would survive a light frost at 32 °F.

The climate record spans 30 years, and the two 32°F 50 % dates are 108 days apart.

How to read the probabilities

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

  • Spring: "10% after June 12" 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 Columbus, MTNumbered nearest stations: 1 — Rapelje, MT — 23 mi; 2 — Nye #2, MT — 30 mi; 3 — Big Timber, MT — 35 mi; 4 — Mystic Lake, MT — 36 mi; 5 — Billings (Logan Airport), MT — 37 mi.25 mi · 40 km1. Rapelje, MT — 23 mi12. Nye #2, MT — 30 mi23. Big Timber, MT — 35 mi34. Mystic Lake, MT — 36 mi45. Billings (Logan Airport), MT — 37 mi5
  1. Rapelje, MT 23 mi (36 km)
  2. Nye #2, MT 30 mi (48 km)
  3. Big Timber, MT 35 mi (57 km)
  4. Mystic Lake, MT 36 mi (57 km)
  5. Billings (Logan Airport), MT 37 mi (59 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: 45.6444, -109.2675.