U.S. Frost Dates by Weather Station

NOAA station USC00201486 · Michigan

Frost Dates for Chatham Experiment Farm 2, MI

NOAA weather station Chatham Experiment Farm 2 (USC00201486), Michigan · elevation 870 ft (265 m) · hardiness zone 5a*

  • Lower-risk planting dateafter June 21only 1 spring in 10 still has a frost later
  • Typical last frostMay 3050% chance of a frost after it
  • Typical first fall frostSeptember 2750% chance of a frost before it
  • Frost-free season119 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Chatham Experiment Farm 2, MISpring: a frost after May 14 in 9 years out of 10, after May 30 in half of the years, after June 21 in 1 year out of 10. Fall: the first frost comes before September 6 in 1 year out of 10, before September 27 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 119 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 30First frost ~Sep 27Frost season at Chatham Experiment Farm 2, MISpring: a frost after May 14 in 9 years out of 10, after May 30 in half of the years, after June 21 in 1 year out of 10. Fall: the first frost comes before September 6 in 1 year out of 10, before September 27 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 119 days.JFMAMJJASONDLast frost ~May 30First frost ~Sep 27
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)June 21September 6
50% (typical)May 30September 27
90% (likely)May 14October 11
Frost-free season (32°F, 50% chance)
119 days
Hard frost (28°F), last in spring, 50% chance after
May 16
Hard frost (28°F), first in fall, 50% chance before
October 9

The last 15 years (2006–2020 normals)

Typical last frost May 26 (4 days earlier than the 30-year normal), typical first fall frost September 30 (3 days later). Frost-free season 125 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 Chatham Experiment Farm 2: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 21, 20% June 11, 30% June 5, 40% June 1, 50% May 30, 60% May 27, 70% May 23, 80% May 20, 90% May 14. Observed last spring frost in recent years: 2021 May 30, 2022 May 24, 2023 June 12, 2024 May 30, 2025 June 1, 2026 May 22.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jul 1Jun 21May 30May 142021: May 302022: May 242023: June 122024: May 302025: June 12026: May 22Fall at Chatham Experiment Farm 2: chance of a frost before this dateFall, chance of a frost before the date: 10% September 6, 20% September 13, 30% September 18, 40% September 23, 50% September 27, 60% October 1, 70% October 3, 80% October 6, 90% October 11. Observed first fall frost in recent years: 2021 October 18, 2022 September 23, 2023 October 12, 2024 October 4, 2025 October 9.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 6Sep 27Oct 112021: October 182022: September 232023: October 122024: October 42025: October 9
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 30October 18
2022May 24September 23
2023June 12October 12
2024May 30October 4
2025June 1October 9
2026May 22season not over yet

What these dates mean

June 21, with a 10% chance of a frost later, is the cautious spring date for setting out tender crops at Chatham Experiment Farm 2. Planting on or after this day gives a gardener a low risk of a light frost damaging delicate seedlings.

The 50% spring date, May 30, indicates an even odds point—there is a 50% chance of a frost later than this date, while the 50% fall date, September 27, marks an even odds point for a frost earlier than that day. The cautious fall date, September 6 with a 10% chance of a frost earlier, signals when tender crops should be finished harvesting to avoid a likely light frost.

Hard-frost dates—May 16 in spring and October 9 in fall—are the median points for a 28 °F frost, which can damage plants more severely than 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 June 21" 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 6" 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 Chatham Experiment Farm 2, MINumbered nearest stations: 1 — Munising, MI — 13 mi; 2 — Marquette (USW00014838), MI — 26 mi; 3 — Marquette (USW00094850), MI — 32 mi; 4 — Manistique, MI — 42 mi; 5 — near Kingsford, MI — 68 mi.MI25 mi · 40 km1. Munising, MI — 13 mi12. Marquette (USW00014838), MI — 26 mi23. Marquette (USW00094850), MI — 32 mi34. Manistique, MI — 42 mi45. near Kingsford, MI — 68 mi5
  1. Munising, MI 13 mi (22 km)
  2. Marquette (USW00014838), MI 26 mi (42 km)
  3. Marquette (USW00094850), MI 32 mi (52 km)
  4. Manistique, MI 42 mi (68 km)
  5. near Kingsford, MI 68 mi (109 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: 46.3414, -86.9242.