U.S. Frost Dates by Weather Station

NOAA station USW00024033 · Montana

Frost Dates for Billings (Logan Airport), MT

NOAA weather station Billings Logan International Airport (USW00024033), Montana · elevation 3581 ft (1092 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 18only 1 spring in 10 still has a frost later
  • Typical last frostMay 450% chance of a frost after it
  • Typical first fall frostOctober 750% chance of a frost before it
  • Frost-free season156 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Billings (Logan Airport), MTSpring: a frost after April 20 in 9 years out of 10, after May 4 in half of the years, after May 18 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 7 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 156 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 4First frost ~Oct 7Frost season at Billings (Logan Airport), MTSpring: a frost after April 20 in 9 years out of 10, after May 4 in half of the years, after May 18 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 7 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 156 days.JFMAMJJASONDLast frost ~May 4First frost ~Oct 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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 18September 26
50% (typical)May 4October 7
90% (likely)April 20October 21
Frost-free season (32°F, 50% chance)
156 days
Hard frost (28°F), last in spring, 50% chance after
April 21
Hard frost (28°F), first in fall, 50% chance before
October 16

The last 15 years (2006–2020 normals)

Typical last frost May 1 (3 days earlier than the 30-year normal), typical first fall frost October 10 (3 days later). Frost-free season 160 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 Billings (Logan Airport): chance of a frost after this dateSpring, chance of a frost after the date: 10% May 18, 20% May 14, 30% May 10, 40% May 7, 50% May 4, 60% May 1, 70% April 29, 80% April 24, 90% April 20. Observed last spring frost in recent years: 2021 May 22, 2022 May 22, 2023 April 28, 2024 May 4, 2025 April 18, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 18May 4Apr 202021: May 222022: May 222023: April 282024: May 42025: April 182026: May 19Fall at Billings (Logan Airport): chance of a frost before this dateFall, chance of a frost before the date: 10% September 26, 20% September 29, 30% October 1, 40% October 4, 50% October 7, 60% October 11, 70% October 14, 80% October 16, 90% October 21. Observed first fall frost in recent years: 2021 October 11, 2022 October 23, 2023 October 14, 2024 October 25, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 26Oct 7Oct 212021: October 112022: October 232023: October 142024: October 252025: October 13
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 22October 11
2022May 22October 23
2023April 28October 14
2024May 4October 25
2025April 18October 13
2026May 19season not over yet

What these dates mean

The 156 days between the 50% dates in Billings (Logan Airport) define the span from the median light-frost date of May 4 to the median light-frost date of October 7. Within those 156 days the likelihood of a light frost is less than 50 %, and the record covers 30 years.

For tender crops the cautious spring date is May 18, when there is only a 10 % chance of a frost later, while the risky early option is April 20 with a 90 % chance. In the fall the cautious date is September 26, offering a 10 % chance of a frost earlier, and the gamble is October 21 with a 90 % chance. The hard-frost 50% dates are April 21 and October 16; a hard frost at 28 °F can damage plant tissue that would survive a light frost at 32 °F, making it a more serious threat.

How to read the probabilities

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

  • Spring: "10% after May 18" 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 26" 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 Billings (Logan Airport), MTNumbered nearest stations: 1 — Billings, MT — 4 mi; 2 — Rapelje, MT — 36 mi; 3 — Columbus, MT — 37 mi; 4 — Roundup, MT — 44 mi; 5 — Yellowtail Dam, MT — 45 mi.25 mi · 40 km1. Billings, MT — 4 mi12. Rapelje, MT — 36 mi23. Columbus, MT — 37 mi34. Roundup, MT — 44 mi45. Yellowtail Dam, MT — 45 mi5
  1. Billings, MT 4 mi (6 km)
  2. Rapelje, MT 36 mi (58 km)
  3. Columbus, MT 37 mi (59 km)
  4. Roundup, MT 44 mi (70 km)
  5. Yellowtail Dam, MT 45 mi (72 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: 45.8069, -108.5422.