U.S. Frost Dates by Weather Station

NOAA station USC00242104 · Montana

Frost Dates for Creston, MT

NOAA weather station Creston (USC00242104), Montana · elevation 2935 ft (895 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 1250% chance of a frost after it
  • Typical first fall frostSeptember 2550% chance of a frost before it
  • Frost-free season134 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Creston, MTSpring: a frost after April 30 in 9 years out of 10, after May 12 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 9 in 1 year out of 10, before September 25 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 134 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 12First frost ~Sep 25Frost season at Creston, MTSpring: a frost after April 30 in 9 years out of 10, after May 12 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 9 in 1 year out of 10, before September 25 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 134 days.JFMAMJJASONDLast frost ~May 12First frost ~Sep 25
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)May 26September 9
50% (typical)May 12September 25
90% (likely)April 30October 8
Frost-free season (32°F, 50% chance)
134 days
Hard frost (28°F), last in spring, 50% chance after
April 28
Hard frost (28°F), first in fall, 50% chance before
October 5

The last 15 years (2006–2020 normals)

Typical last frost May 11 (1 day earlier than the 30-year normal), typical first fall frost September 26 (1 day later). Frost-free season 136 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 Creston: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 21, 30% May 18, 40% May 15, 50% May 12, 60% May 10, 70% May 7, 80% May 4, 90% April 30. Observed last spring frost in recent years: 2021 May 29, 2022 May 22, 2023 April 28, 2024 May 19, 2025 May 7, 2026 May 21.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 12Apr 302021: May 292022: May 222023: April 282024: May 192025: May 72026: May 21Fall at Creston: chance of a frost before this dateFall, chance of a frost before the date: 10% September 9, 20% September 16, 30% September 20, 40% September 23, 50% September 25, 60% September 27, 70% September 30, 80% October 3, 90% October 8. Observed first fall frost in recent years: 2021 September 17, 2022 September 21, 2023 October 7, 2024 September 30, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 9Sep 25Oct 82021: September 172022: September 212023: October 72024: September 302025: 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
2021May 29September 17
2022May 22September 21
2023April 28October 7
2024May 19September 30
2025May 7October 6
2026May 21season not over yet

What these dates mean

Creston enjoys 134 days between the 32°F 50% dates, offering a window for planting, growth, and harvest in this zone. The 50% dates—May 12 in spring and September 25 in fall—mark the median point where a light frost is equally likely to occur later (spring) or earlier (fall); they are not frost dates themselves. Gardeners who prefer low risk should aim to set out tender crops after the cautious spring date of May 26 and should finish harvesting tender crops by the cautious fall date of September 9; attempting tender crops as early as April 30 or as late as October 8 carries a 90% chance of frost and is a gamble. The hard-frost median dates are April 28 and October 5, and a 28°F frost can kill or severely damage plants that would otherwise survive a 32°F light frost.

How to read the probabilities

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

  • Spring: "10% after May 26" 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 9" 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 Creston, MTNumbered nearest stations: 1 — near Kalispell, MT — 10 mi; 2 — West Glacier, MT — 23 mi; 3 — Libby Dam (Base), MT — 57 mi; 4 — Lindbergh Lake, MT — 57 mi; 5 — near Thompson Falls, MT — 70 mi.MTID25 mi · 40 km1. near Kalispell, MT — 10 mi12. West Glacier, MT — 23 mi23. Libby Dam (Base), MT — 57 mi34. Lindbergh Lake, MT — 57 mi45. near Thompson Falls, MT — 70 mi5
  1. near Kalispell, MT 10 mi (16 km)
  2. West Glacier, MT 23 mi (36 km)
  3. Libby Dam (Base), MT 57 mi (91 km)
  4. Lindbergh Lake, MT 57 mi (92 km)
  5. near Thompson Falls, MT 70 mi (113 km)

Sources

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

Station coordinates: 48.1881, -114.1339.