U.S. Frost Dates by Weather Station

NOAA station USC00206680 · Michigan

Frost Dates for Port Huron, MI

NOAA weather station Port Huron (USC00206680), Michigan · elevation 590 ft (180 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 4only 1 spring in 10 still has a frost later
  • Typical last frostApril 1950% chance of a frost after it
  • Typical first fall frostNovember 350% chance of a frost before it
  • Frost-free season196 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Port Huron, MISpring: a frost after April 7 in 9 years out of 10, after April 19 in half of the years, after May 4 in 1 year out of 10. Fall: the first frost comes before October 20 in 1 year out of 10, before November 3 in half of the years, before November 16 in 9 years out of 10. Typical frost-free season: 196 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 19First frost ~Nov 3Frost season at Port Huron, MISpring: a frost after April 7 in 9 years out of 10, after April 19 in half of the years, after May 4 in 1 year out of 10. Fall: the first frost comes before October 20 in 1 year out of 10, before November 3 in half of the years, before November 16 in 9 years out of 10. Typical frost-free season: 196 days.JFMAMJJASONDLast frost ~Apr 19First frost ~Nov 3
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 4October 20
50% (typical)April 19November 3
90% (likely)April 7November 16
Frost-free season (32°F, 50% chance)
196 days
Hard frost (28°F), last in spring, 50% chance after
April 7
Hard frost (28°F), first in fall, 50% chance before
November 12

The last 15 years (2006–2020 normals)

Typical last frost April 20 (1 day later than the 30-year normal), typical first fall frost November 4 (1 day later). Frost-free season 197 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 Port Huron: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 4, 20% April 29, 30% April 25, 40% April 21, 50% April 19, 60% April 17, 70% April 14, 80% April 10, 90% April 7. Observed last spring frost in recent years: 2021 May 1, 2022 April 28, 2023 April 8, 2024 April 26, 2025 April 17, 2026 May 12.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 4Apr 19Apr 72021: May 12022: April 282023: April 82024: April 262025: April 172026: May 12Fall at Port Huron: chance of a frost before this dateFall, chance of a frost before the date: 10% October 20, 20% October 25, 30% October 30, 40% November 1, 50% November 3, 60% November 5, 70% November 8, 80% November 11, 90% November 16. Observed first fall frost in recent years: 2021 November 3, 2022 November 13, 2023 October 31, 2024 October 27, 2025 November 2.Fall: first frostChance of a frost before this date10%50%90%Nov 1Oct 20Nov 3Nov 162021: November 32022: November 132023: October 312024: October 272025: November 2
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 28November 13
2023April 8October 31
2024April 26October 27
2025April 17November 2
2026May 12season not over yet

What these dates mean

October 20 marks the cautious fall date in Port Huron for finishing the harvest of tender crops; only a 10 % chance exists that a light frost has arrived earlier. The 50 % date is November 3, indicating a 50 % chance of a light frost earlier than this date, while November 16 carries a 90 % chance that a light frost will already be present, making a late harvest a gamble.

In spring, the cautious date for setting out tender crops is May 4, when there is just a 10 % chance of a light frost later. The 50 % date is April 19, showing a 50 % chance of a light frost later than this date, and April 7 carries a 90 % chance, a risky early planting. The hard-frost 50 % dates are April 7 and November 12; a hard frost at 28 °F can damage plants that would survive a light frost at 32 °F, making it a more critical threshold.

How to read the probabilities

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

  • Spring: "10% after May 4" 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 20" 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 Port Huron, MINumbered nearest stations: 1 — near Detroit, MI — 49 mi; 2 — Harbor Beach, MI — 60 mi; 3 — Dearborn, MI — 61 mi; 4 — Bad Axe, MI — 64 mi; 5 — Detroit (Metro Airport), MI — 69 mi.MI50 mi · 80 km1. near Detroit, MI — 49 mi12. Harbor Beach, MI — 60 mi23. Dearborn, MI — 61 mi34. Bad Axe, MI — 64 mi45. Detroit (Metro Airport), MI — 69 mi5
  1. near Detroit, MI 49 mi (79 km)
  2. Harbor Beach, MI 60 mi (97 km)
  3. Dearborn, MI 61 mi (99 km)
  4. Bad Axe, MI 64 mi (104 km)
  5. Detroit (Metro Airport), 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: 42.975, -82.4194.