U.S. Frost Dates by Weather Station

NOAA station USC00245043 · Montana

Frost Dates for Lindbergh Lake, MT

NOAA weather station Lindbergh Lake (USC00245043), Montana · elevation 4320 ft (1317 m) · hardiness zone 5a*

  • Lower-risk planting dateafter June 7only 1 spring in 10 still has a frost later
  • Typical last frostMay 2050% chance of a frost after it
  • Typical first fall frostSeptember 2250% chance of a frost before it
  • Frost-free season120 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Lindbergh Lake, MTSpring: a frost after May 7 in 9 years out of 10, after May 20 in half of the years, after June 7 in 1 year out of 10. Fall: the first frost comes before September 5 in 1 year out of 10, before September 22 in half of the years, before October 5 in 9 years out of 10. Typical frost-free season: 120 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 20First frost ~Sep 22Frost season at Lindbergh Lake, MTSpring: a frost after May 7 in 9 years out of 10, after May 20 in half of the years, after June 7 in 1 year out of 10. Fall: the first frost comes before September 5 in 1 year out of 10, before September 22 in half of the years, before October 5 in 9 years out of 10. Typical frost-free season: 120 days.JFMAMJJASONDLast frost ~May 20First frost ~Sep 22
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 7September 5
50% (typical)May 20September 22
90% (likely)May 7October 5
Frost-free season (32°F, 50% chance)
120 days
Hard frost (28°F), last in spring, 50% chance after
May 3
Hard frost (28°F), first in fall, 50% chance before
October 4

The last 15 years (2006–2020 normals)

Typical last frost May 21 (1 day later than the 30-year normal), typical first fall frost September 22. Frost-free season 124 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 Lindbergh Lake: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 7, 20% June 1, 30% May 28, 40% May 24, 50% May 20, 60% May 17, 70% May 14, 80% May 11, 90% May 7. Observed last spring frost in recent years: 2021 June 11, 2022 May 20, 2023 April 28, 2024 May 20, 2025 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 7May 20May 72021: June 112022: May 202023: April 282024: May 202025: May 19Fall at Lindbergh Lake: chance of a frost before this dateFall, chance of a frost before the date: 10% September 5, 20% September 13, 30% September 16, 40% September 19, 50% September 22, 60% September 25, 70% September 28, 80% October 1, 90% October 5. Observed first fall frost in recent years: 2021 September 17, 2022 September 10, 2023 October 25, 2024 October 1, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Nov 1Sep 5Sep 22Oct 52021: September 172022: September 102023: October 252024: October 12025: 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
2021June 11September 17
2022May 20September 10
2023April 28October 25
2024May 20October 1
2025May 19October 6
2026incomplete recordseason not over yet

What these dates mean

June 7 is the cautious spring light-frost date; there is only a 10 % chance of a frost later than that day, so gardeners can plan to set out tender crops after June 7 with relatively low risk.

The 50 % date is May 20, indicating a 50 % chance of a frost later than this date, while the 50 % date is September 22, indicating a 50 % chance of a frost earlier than this date. The cautious fall light-frost date is September 5, when there is just a 10 % chance that a frost has already arrived, allowing growers to finish harvesting tender crops by then. A hard frost at 28 °F, reflected by the 50 % dates May 3 and October 4, can damage plant tissue more severely than a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after June 7" 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 5" 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 Lindbergh Lake, MTNumbered nearest stations: 1 — Creston, MT — 57 mi; 2 — Stevensville, MT — 64 mi; 3 — near Kalispell, MT — 67 mi; 4 — Choteau, MT — 76 mi; 5 — West Glacier, MT — 76 mi.MTID50 mi · 80 km1. Creston, MT — 57 mi12. Stevensville, MT — 64 mi23. near Kalispell, MT — 67 mi34. Choteau, MT — 76 mi45. West Glacier, MT — 76 mi5
  1. Creston, MT 57 mi (92 km)
  2. Stevensville, MT 64 mi (104 km)
  3. near Kalispell, MT 67 mi (108 km)
  4. Choteau, MT 76 mi (123 km)
  5. West Glacier, MT 76 mi (123 km)

Sources

* Hardiness zone 5a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 47.4083, -113.7125.