U.S. Frost Dates by Weather Station

NOAA station USC00203823 · Michigan

Frost Dates for Hillsdale, MI

NOAA weather station Hillsdale (USC00203823), Michigan · elevation 1080 ft (329 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 19only 1 spring in 10 still has a frost later
  • Typical last frostMay 350% chance of a frost after it
  • Typical first fall frostOctober 1250% chance of a frost before it
  • Frost-free season161 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Hillsdale, MISpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 19 in 1 year out of 10. Fall: the first frost comes before September 29 in 1 year out of 10, before October 12 in half of the years, before October 27 in 9 years out of 10. Typical frost-free season: 161 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 3First frost ~Oct 12Frost season at Hillsdale, MISpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 19 in 1 year out of 10. Fall: the first frost comes before September 29 in 1 year out of 10, before October 12 in half of the years, before October 27 in 9 years out of 10. Typical frost-free season: 161 days.JFMAMJJASONDLast frost ~May 3First frost ~Oct 12
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 19September 29
50% (typical)May 3October 12
90% (likely)April 20October 27
Frost-free season (32°F, 50% chance)
161 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
October 26

The last 15 years (2006–2020 normals)

Typical last frost May 3 (same as the 30-year normal), typical first fall frost October 17 (5 days later). Frost-free season 166 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 Hillsdale: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 19, 20% May 14, 30% May 10, 40% May 6, 50% May 3, 60% April 30, 70% April 28, 80% April 24, 90% April 20. Observed last spring frost in recent years: 2021 May 13, 2022 April 27, 2023 April 26, 2024 April 25, 2025 May 9, 2026 May 3.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 19May 3Apr 202021: May 132022: April 272023: April 262024: April 252025: May 92026: May 3Fall at Hillsdale: chance of a frost before this dateFall, chance of a frost before the date: 10% September 29, 20% October 3, 30% October 6, 40% October 10, 50% October 12, 60% October 15, 70% October 19, 80% October 22, 90% October 27. Observed first fall frost in recent years: 2021 October 23, 2022 October 7, 2023 October 22, 2024 October 18, 2025 October 25.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 29Oct 12Oct 272021: October 232022: October 72023: October 222024: October 182025: October 25
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 23
2022April 27October 7
2023April 26October 22
2024April 25October 18
2025May 9October 25
2026May 3season not over yet

What these dates mean

May 19, which carries a 10% chance of a later light frost, is the cautious spring date that lets a gardener plan to set out tender crops.

The 50% light-frost date is May 3; at that point there is an even chance of a frost occurring later in spring. The median hard-frost date in spring is April 23. In fall, the 50% light-frost date is October 12 and the median hard-frost date is October 26. September 29, which has a 10% chance of an earlier light frost, is the cautious fall date for finishing harvest of tender crops. The record spans 26 years, and there are 161 days between the two 32°F 50% dates, defining the frost-free interval.

A hard frost at 28 °F can injure plants that survive a 32 °F light frost, making it a more severe threat.

How to read the probabilities

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

  • Spring: "10% after May 19" 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 29" 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 Hillsdale, MINumbered nearest stations: 1 — near Coldwater, MI — 18 mi; 2 — near Jackson, MI — 25 mi; 3 — Angola, IN — 27 mi; 4 — Adrian, MI — 32 mi; 5 — Wauseon, OH — 39 mi.OHIN25 mi · 40 km1. near Coldwater, MI — 18 mi12. near Jackson, MI — 25 mi23. Angola, IN — 27 mi34. Adrian, MI — 32 mi45. Wauseon, OH — 39 mi5
  1. near Coldwater, MI 18 mi (29 km)
  2. near Jackson, MI 25 mi (40 km)
  3. Angola, IN 27 mi (43 km)
  4. Adrian, MI 32 mi (52 km)
  5. Wauseon, OH 39 mi (62 km)

Sources

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

Station coordinates: 41.9353, -84.6411.