U.S. Frost Dates by Weather Station

NOAA station USC00203585 · Michigan

Frost Dates for Harbor Beach, MI

NOAA weather station Harbor Beach 1 SSE (USC00203585), Michigan · elevation 595 ft (181 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 2450% chance of a frost before it
  • Frost-free season173 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Harbor Beach, MISpring: a frost after April 19 in 9 years out of 10, after May 2 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before October 7 in 1 year out of 10, before October 24 in half of the years, before November 6 in 9 years out of 10. Typical frost-free season: 173 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 24Frost season at Harbor Beach, MISpring: a frost after April 19 in 9 years out of 10, after May 2 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before October 7 in 1 year out of 10, before October 24 in half of the years, before November 6 in 9 years out of 10. Typical frost-free season: 173 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 24
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 17October 7
50% (typical)May 2October 24
90% (likely)April 19November 6
Frost-free season (32°F, 50% chance)
173 days
Hard frost (28°F), last in spring, 50% chance after
April 20
Hard frost (28°F), first in fall, 50% chance before
November 3

The last 15 years (2006–2020 normals)

Typical last frost May 3 (1 day later than the 30-year normal), typical first fall frost October 25 (1 day later). Frost-free season 174 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 Harbor Beach: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 11, 30% May 8, 40% May 5, 50% May 2, 60% April 30, 70% April 27, 80% April 24, 90% April 19. Observed last spring frost in recent years: 2021 May 1, 2022 April 29, 2023 May 18, 2024 April 26, 2025 April 18, 2026 May 12.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 2Apr 192021: May 12022: April 292023: May 182024: April 262025: April 182026: May 12Fall at Harbor Beach: chance of a frost before this dateFall, chance of a frost before the date: 10% October 7, 20% October 14, 30% October 18, 40% October 21, 50% October 24, 60% October 26, 70% October 29, 80% November 1, 90% November 6. Observed first fall frost in recent years: 2021 November 3, 2022 November 13, 2023 October 31, 2024 October 27, 2025 November 10.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 7Oct 24Nov 62021: November 32022: November 132023: October 312024: October 272025: November 10
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 1November 3
2022April 29November 13
2023May 18October 31
2024April 26October 27
2025April 18November 10
2026May 12season not over yet

What these dates mean

The 173 days between the 50% dates in Harbor Beach frame the period most gardeners watch. The 50% date is May 2; there is a 50% chance of a frost later than this date in spring. The fall 50% date is October 24; there is a 50% chance of a frost earlier than this date.

For a cautious spring schedule the tender-crop window begins on May 17, when only a 10% chance of a light frost remains. In the fall the cautious date to finish tender crops is October 7, also with a 10% chance of a frost occurring earlier. The hard-frost median dates are April 20 and November 3; a hard frost at 28 °F poses a greater threat than a light frost at 32 °F because the lower temperature can kill plant tissue that would survive a milder chill.

How to read the probabilities

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

  • Spring: "10% after May 17" 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 October 7" 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 Harbor Beach, MINumbered nearest stations: 1 — Bad Axe, MI — 18 mi; 2 — East Tawas, MI — 53 mi; 3 — Port Huron, MI — 60 mi; 4 — Standish, MI — 64 mi; 5 — Hale Loud Dam, MI — 69 mi.MI50 mi · 80 km1. Bad Axe, MI — 18 mi12. East Tawas, MI — 53 mi23. Port Huron, MI — 60 mi34. Standish, MI — 64 mi45. Hale Loud Dam, MI — 69 mi5
  1. Bad Axe, MI 18 mi (28 km)
  2. East Tawas, MI 53 mi (85 km)
  3. Port Huron, MI 60 mi (97 km)
  4. Standish, MI 64 mi (102 km)
  5. Hale Loud Dam, MI 69 mi (111 km)

Sources

* Hardiness zone 6b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 43.8322, -82.6428.