U.S. Frost Dates by Weather Station

NOAA station USC00200718 · Michigan

Frost Dates for Bergland Dam, MI

NOAA weather station Bergland Dam (USC00200718), Michigan · elevation 1300 ft (396 m) · hardiness zone 4a*

  • Lower-risk planting dateafter June 8only 1 spring in 10 still has a frost later
  • Typical last frostMay 2650% chance of a frost after it
  • Typical first fall frostSeptember 2750% chance of a frost before it
  • Frost-free season123 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Bergland Dam, MISpring: a frost after May 9 in 9 years out of 10, after May 26 in half of the years, after June 8 in 1 year out of 10. Fall: the first frost comes before September 10 in 1 year out of 10, before September 27 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 123 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 26First frost ~Sep 27Frost season at Bergland Dam, MISpring: a frost after May 9 in 9 years out of 10, after May 26 in half of the years, after June 8 in 1 year out of 10. Fall: the first frost comes before September 10 in 1 year out of 10, before September 27 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 123 days.JFMAMJJASONDLast frost ~May 26First 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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 8September 10
50% (typical)May 26September 27
90% (likely)May 9October 9
Frost-free season (32°F, 50% chance)
123 days
Hard frost (28°F), last in spring, 50% chance after
May 12
Hard frost (28°F), first in fall, 50% chance before
October 7

The last 15 years (2006–2020 normals)

Typical last frost May 22 (4 days earlier than the 30-year normal), typical first fall frost October 1 (4 days later). Frost-free season 129 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 Bergland Dam: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 8, 20% June 3, 30% May 31, 40% May 28, 50% May 26, 60% May 22, 70% May 19, 80% May 15, 90% May 9. Observed last spring frost in recent years: 2021 May 31, 2022 May 23, 2023 May 26, 2025 May 25, 2026 May 22.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 8May 26May 92021: May 312022: May 232023: May 262025: May 252026: May 22Fall at Bergland Dam: chance of a frost before this dateFall, chance of a frost before the date: 10% September 10, 20% September 16, 30% September 21, 40% September 24, 50% September 27, 60% October 1, 70% October 2, 80% October 5, 90% October 9. Observed first fall frost in recent years: 2021 October 17, 2022 September 23, 2023 October 8, 2024 October 4, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 10Sep 27Oct 92021: October 172022: September 232023: October 82024: October 42025: October 8
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 31October 17
2022May 23September 23
2023May 26October 8
2024incomplete recordOctober 4
2025May 25October 8
2026May 22season not over yet

What these dates mean

The 123 days between the 50% dates in Bergland Dam frame the span in which light-frost risk balances at 50 %. The 50% date is May 26 in spring and September 27 in fall; a gardener can expect an even chance of a frost occurring later than May 26 and earlier than September 27.

For a cautious spring schedule the 10 %-chance date of June 8 is used to set out tender crops, while the 10 %-chance fall date of September 10 is the cautious date to finish harvesting tender crops. The 90 %-chance dates of May 9 and October 9 represent gambles. The hard-frost 50% dates are May 12 and October 7, and a hard frost at 28 °F can injure plants that survive a light frost at 32 °F, making its timing more critical for protecting crops.

How to read the probabilities

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

  • Spring: "10% after June 8" 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 10" 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 Bergland Dam, MINumbered nearest stations: 1 — Ironwood, MI — 32 mi; 2 — Hurley, WI — 32 mi; 3 — Stambaugh, MI — 57 mi; 4 — Madeline Island, WI — 59 mi; 5 — Hancock, MI — 64 mi.MIWI25 mi · 40 km1. Ironwood, MI — 32 mi12. Hurley, WI — 32 mi23. Stambaugh, MI — 57 mi34. Madeline Island, WI — 59 mi45. Hancock, MI — 64 mi5
  1. Ironwood, MI 32 mi (51 km)
  2. Hurley, WI 32 mi (51 km)
  3. Stambaugh, MI 57 mi (92 km)
  4. Madeline Island, WI 59 mi (95 km)
  5. Hancock, MI 64 mi (104 km)

Sources

* Hardiness zone 4a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 46.5869, -89.5475.