U.S. Frost Dates by Weather Station

NOAA station USC00245603 · Montana

Frost Dates for Melville, MT

NOAA weather station Melville 4 W (USC00245603), Montana · elevation 5365 ft (1635 m) · hardiness zone 4b*

  • Lower-risk planting dateafter June 27only 1 spring in 10 still has a frost later
  • Typical last frostJune 950% chance of a frost after it
  • Typical first fall frostSeptember 750% chance of a frost before it
  • Frost-free season88 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Melville, MTSpring: a frost after May 26 in 9 years out of 10, after June 9 in half of the years, after June 27 in 1 year out of 10. Fall: the first frost comes before August 21 in 1 year out of 10, before September 7 in half of the years, before September 23 in 9 years out of 10. Typical frost-free season: 88 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Jun 9First frost ~Sep 7Frost season at Melville, MTSpring: a frost after May 26 in 9 years out of 10, after June 9 in half of the years, after June 27 in 1 year out of 10. Fall: the first frost comes before August 21 in 1 year out of 10, before September 7 in half of the years, before September 23 in 9 years out of 10. Typical frost-free season: 88 days.JFMAMJJASONDLast frost ~Jun 9First frost ~Sep 7
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 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 27August 21
50% (typical)June 9September 7
90% (likely)May 26September 23
Frost-free season (32°F, 50% chance)
88 days
Hard frost (28°F), last in spring, 50% chance after
May 24
Hard frost (28°F), first in fall, 50% chance before
September 22

The last 15 years (2006–2020 normals)

Typical last frost June 2 (7 days earlier than the 30-year normal), typical first fall frost September 18 (11 days later). Frost-free season 108 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 Melville: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 27, 20% June 20, 30% June 16, 40% June 12, 50% June 9, 60% June 6, 70% June 3, 80% May 31, 90% May 26. Observed last spring frost in recent years: 2021 May 30, 2022 June 26, 2023 June 22, 2024 June 19, 2025 June 23, 2026 June 14.Spring: last frostChance of a frost after this date10%50%90%Jun 1Jul 1Jun 27Jun 9May 262021: May 302022: June 262023: June 222024: June 192025: June 232026: June 14Fall at Melville: chance of a frost before this dateFall, chance of a frost before the date: 10% August 21, 20% August 27, 30% August 31, 40% September 3, 50% September 7, 60% September 10, 70% September 13, 80% September 17, 90% September 23. Observed first fall frost in recent years: 2021 September 17, 2022 September 10, 2023 September 29, 2024 September 21, 2025 October 5.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Aug 21Sep 7Sep 232021: September 172022: September 102023: September 292024: September 212025: October 5
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
2022June 26September 10
2023June 22September 29
2024June 19September 21
2025June 23October 5
2026June 14season not over yet

What these dates mean

August 21 is the cautious fall date in Melville for finishing the harvest of tender crops; only a 10% chance exists that a light frost has arrived earlier. The 50% date is September 7, when there is a 50% chance of a light frost earlier than this date, and September 23 carries a 90% chance, making a late tender-crop harvest a gamble.

June 27 is the cautious spring date for setting out tender crops, with only a 10% chance of a light frost later than that day. The 50% date is June 9, when there is a 50% chance of a light frost later than this date, while May 26 has a 90% chance, indicating a gamble for early planting.

Hard frost, defined at 28°F, is more destructive than a 32°F light frost; the median hard-frost dates are May 24 in spring and September 22 in fall, reminding gardeners that the lower temperature poses a greater risk to plant tissue. The record spans 25 years.

How to read the probabilities

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

  • Spring: "10% after June 27" 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 21" 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 Melville, MTNumbered nearest stations: 1 — Big Timber, MT — 19 mi; 2 — Rapelje, MT — 39 mi; 3 — Ryegate, MT — 45 mi; 4 — Nye #2, MT — 48 mi; 5 — Columbus, MT — 49 mi.MT25 mi · 40 km1. Big Timber, MT — 19 mi12. Rapelje, MT — 39 mi23. Ryegate, MT — 45 mi34. Nye #2, MT — 48 mi45. Columbus, MT — 49 mi5
  1. Big Timber, MT 19 mi (31 km)
  2. Rapelje, MT 39 mi (63 km)
  3. Ryegate, MT 45 mi (72 km)
  4. Nye #2, MT 48 mi (77 km)
  5. Columbus, MT 49 mi (79 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: 46.1047, -110.05.