U.S. Frost Dates by Weather Station

NOAA station USC00208800 · Michigan

Frost Dates for West Branch, MI

NOAA weather station West Branch 3 SE (USC00208800), Michigan · elevation 885 ft (270 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 29only 1 spring in 10 still has a frost later
  • Typical last frostMay 1550% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season143 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at West Branch, MISpring: a frost after April 29 in 9 years out of 10, after May 15 in half of the years, after May 29 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 143 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 15First frost ~Oct 4Frost season at West Branch, MISpring: a frost after April 29 in 9 years out of 10, after May 15 in half of the years, after May 29 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 143 days.JFMAMJJASONDLast frost ~May 15First frost ~Oct 4
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 29September 21
50% (typical)May 15October 4
90% (likely)April 29October 17
Frost-free season (32°F, 50% chance)
143 days
Hard frost (28°F), last in spring, 50% chance after
May 1
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost May 11 (4 days earlier than the 30-year normal), typical first fall frost October 8 (4 days later). Frost-free season 150 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 West Branch: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 29, 20% May 24, 30% May 20, 40% May 17, 50% May 15, 60% May 11, 70% May 7, 80% May 3, 90% April 29. Observed last spring frost in recent years: 2021 May 13, 2022 May 8, 2023 May 26, 2024 April 27, 2025 May 9, 2026 May 12.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 29May 15Apr 292021: May 132022: May 82023: May 262024: April 272025: May 92026: May 12Fall at West Branch: chance of a frost before this dateFall, chance of a frost before the date: 10% September 21, 20% September 26, 30% September 29, 40% October 1, 50% October 4, 60% October 7, 70% October 9, 80% October 12, 90% October 17. Observed first fall frost in recent years: 2021 October 22, 2022 September 29, 2023 October 12, 2024 October 9, 2025 October 9.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 21Oct 4Oct 172021: October 222022: September 292023: October 122024: October 92025: 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 13October 22
2022May 8September 29
2023May 26October 12
2024April 27October 9
2025May 9October 9
2026May 12season not over yet

What these dates mean

The 143 days between the 50% dates in West Branch, May 15 and October 4, frame the period when light frosts (32 °F) are equally likely to have occurred or not. For a gardener, this interval marks the span in which tender crops can be managed with the lowest overall frost risk, though individual decisions still depend on the specific probability thresholds.

In spring the cautious date for setting out tender crops is May 29, when there is only a 10 % chance of a light frost later; planting before April 29 carries a 90 % gamble. In fall the cautious date to finish harvesting tender crops is September 21, with a 10 % chance of a light frost earlier, while waiting until October 17 involves a 90 % gamble.

A hard frost, defined at 28 °F, is more consequential than a light frost because the lower temperature can damage plant tissue that survives a 32 °F event; the median hard-frost dates are May 1 and October 17.

How to read the probabilities

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

  • Spring: "10% after May 29" 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 21" 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 West Branch, MINumbered nearest stations: 1 — Standish, MI — 22 mi; 2 — Gladwin, MI — 24 mi; 3 — near Houghton Lake, MI — 24 mi; 4 — Hale Loud Dam, MI — 28 mi; 5 — East Tawas, MI — 35 mi.25 mi · 40 km1. Standish, MI — 22 mi12. Gladwin, MI — 24 mi23. near Houghton Lake, MI — 24 mi34. Hale Loud Dam, MI — 28 mi45. East Tawas, MI — 35 mi5
  1. Standish, MI 22 mi (36 km)
  2. Gladwin, MI 24 mi (39 km)
  3. near Houghton Lake, MI 24 mi (39 km)
  4. Hale Loud Dam, MI 28 mi (45 km)
  5. East Tawas, MI 35 mi (56 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: 44.2542, -84.2011.