U.S. Frost Dates by Weather Station

NOAA station USC00241984 · Montana

Frost Dates for Content, MT

NOAA weather station Content 4 NNE (USC00241984), Montana · elevation 2325 ft (709 m) · hardiness zone 3b*

  • Lower-risk planting dateafter June 8only 1 spring in 10 still has a frost later
  • Typical last frostMay 2550% chance of a frost after it
  • Typical first fall frostSeptember 1450% chance of a frost before it
  • Frost-free season110 daystypical year, 32°F
  • Hardiness zone3bcalculated*

The year at a glance

Frost season at Content, MTSpring: a frost after May 11 in 9 years out of 10, after May 25 in half of the years, after June 8 in 1 year out of 10. Fall: the first frost comes before August 29 in 1 year out of 10, before September 14 in half of the years, before September 27 in 9 years out of 10. Typical frost-free season: 110 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 25First frost ~Sep 14Frost season at Content, MTSpring: a frost after May 11 in 9 years out of 10, after May 25 in half of the years, after June 8 in 1 year out of 10. Fall: the first frost comes before August 29 in 1 year out of 10, before September 14 in half of the years, before September 27 in 9 years out of 10. Typical frost-free season: 110 days.JFMAMJJASONDLast frost ~May 25First 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.

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 8August 29
50% (typical)May 25September 14
90% (likely)May 11September 27
Frost-free season (32°F, 50% chance)
110 days
Hard frost (28°F), last in spring, 50% chance after
May 14
Hard frost (28°F), first in fall, 50% chance before
September 24

The last 15 years (2006–2020 normals)

Typical last frost May 23 (2 days earlier than the 30-year normal), typical first fall frost September 16 (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 Content: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 8, 20% June 3, 30% May 31, 40% May 28, 50% May 25, 60% May 22, 70% May 19, 80% May 16, 90% May 11. Observed last spring frost in recent years: 2021 May 21, 2022 June 1, 2023 April 23, 2024 May 31, 2025 May 14.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 8May 25May 112021: May 212022: June 12023: April 232024: May 312025: May 14Fall at Content: chance of a frost before this dateFall, chance of a frost before the date: 10% August 29, 20% September 4, 30% September 7, 40% September 11, 50% September 14, 60% September 17, 70% September 20, 80% September 23, 90% September 27. Observed first fall frost in recent years: 2021 September 16, 2022 September 9, 2023 October 6, 2024 September 29, 2025 September 3.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Aug 29Sep 14Sep 272021: September 162022: September 92023: October 62024: September 292025: September 3
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 21September 16
2022June 1September 9
2023April 23October 6
2024May 31September 29
2025May 14September 3
2026incomplete recordseason not over yet

What these dates mean

The 110 days between the 50% dates of May 25 and September 14 in Content, Montana outline the window when the chance of a light frost is roughly even, providing gardeners a central period to plan activities. The 50% date of May 25 marks the point at which there is an even chance of a light frost later in spring, while September 14 marks the point at which there is an even chance of a light frost earlier in fall.

For a cautious approach, tender crops are best set out after the June 8 date, which carries only a 10 % chance of a later light frost, and are best finished by the August 29 date, which carries only a 10 % chance of an earlier light frost. A hard frost at 28 °F poses a greater threat than a light frost at 32 °F, so the median hard-frost dates of May 14 and September 24 signal when lethal cold becomes a real possibility.

How to read the probabilities

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

  • Spring: "10% after June 8" 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 August 29" 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 Content, MTNumbered nearest stations: 1 — Malta, MT — 26 mi; 2 — Saco, MT — 28 mi; 3 — Glasgow #2, MT — 42 mi; 4 — Glasgow, MT — 43 mi; 5 — Fort Peck Power Plant, MT — 52 mi.MT25 mi · 40 km1. Malta, MT — 26 mi12. Saco, MT — 28 mi23. Glasgow #2, MT — 42 mi34. Glasgow, MT — 43 mi45. Fort Peck Power Plant, MT — 52 mi5
  1. Malta, MT 26 mi (42 km)
  2. Saco, MT 28 mi (45 km)
  3. Glasgow #2, MT 42 mi (67 km)
  4. Glasgow, MT 43 mi (69 km)
  5. Fort Peck Power Plant, MT 52 mi (83 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: 48.0803, -107.525.