U.S. Frost Dates by Weather Station

NOAA station USC00204090 · Michigan

Frost Dates near Kingsford, MI

NOAA weather station Iron Mountain-Kingsford WWTP (USC00204090), Michigan · elevation 1071 ft (326 m) · hardiness zone 4b*

Kingsford is the nearest town to the station (0.9 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter May 31only 1 spring in 10 still has a frost later
  • Typical last frostMay 1750% chance of a frost after it
  • Typical first fall frostOctober 150% chance of a frost before it
  • Frost-free season135 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season near Kingsford, MISpring: a frost after May 2 in 9 years out of 10, after May 17 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before October 1 in half of the years, before October 13 in 9 years out of 10. Typical frost-free season: 135 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 17First frost ~Oct 1Frost season near Kingsford, MISpring: a frost after May 2 in 9 years out of 10, after May 17 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before October 1 in half of the years, before October 13 in 9 years out of 10. Typical frost-free season: 135 days.JFMAMJJASONDLast frost ~May 17First frost ~Oct 1
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.Today

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 31September 17
50% (typical)May 17October 1
90% (likely)May 2October 13
Frost-free season (32°F, 50% chance)
135 days
Hard frost (28°F), last in spring, 50% chance after
May 4
Hard frost (28°F), first in fall, 50% chance before
October 11

The last 15 years (2006–2020 normals)

Typical last frost May 15 (2 days earlier than the 30-year normal), typical first fall frost October 5 (4 days later). Frost-free season 142 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 near Kingsford: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 31, 20% May 26, 30% May 23, 40% May 20, 50% May 17, 60% May 14, 70% May 11, 80% May 7, 90% May 2. Observed last spring frost in recent years: 2021 May 29, 2022 May 23, 2023 May 26, 2024 May 10, 2025 May 9, 2026 May 21.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 31May 17May 22021: May 292022: May 232023: May 262024: May 102025: May 92026: May 21Fall near Kingsford: chance of a frost before this dateFall, chance of a frost before the date: 10% September 17, 20% September 22, 30% September 25, 40% September 28, 50% October 1, 60% October 3, 70% October 5, 80% October 9, 90% October 13. Observed first fall frost in recent years: 2021 October 22, 2022 September 23, 2023 October 7, 2024 October 9, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 17Oct 1Oct 132021: October 222022: September 232023: October 72024: October 92025: 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 29October 22
2022May 23September 23
2023May 26October 7
2024May 10October 9
2025May 9October 8
2026May 21season not over yet

What these dates mean

The cautious fall date for finishing the harvest in the Kingsford area is September 17, when there is only a 10% chance a light frost has arrived.

The 50% spring light-frost date is May 17; at that point a gardener faces an even chance of a frost later. The 50% fall light-frost date is October 1, giving an even chance of a frost earlier. Hard-frost median dates are May 4 and October 11, and a hard frost at 28 °F can damage plants that survive a 32 °F light frost, so it is a more severe risk.

For tender crops the cautious spring date is May 31, with only a 10% chance of a later frost, while the cautious fall date is September 17, with only a 10% chance that a frost has already occurred.

How to read the probabilities

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

  • Spring: "10% after May 31" 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 17" 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 Kingsford, MINumbered nearest stations: 1 — Stambaugh, MI — 32 mi; 2 — Marquette (USW00094850), MI — 58 mi; 3 — Oconto, WI — 62 mi; 4 — Marquette (USW00014838), MI — 62 mi; 5 — Washington Island, WI — 65 mi.MIWI50 mi · 80 km1. Stambaugh, MI — 32 mi12. Marquette (USW00094850), MI — 58 mi23. Oconto, WI — 62 mi34. Marquette (USW00014838), MI — 62 mi45. Washington Island, WI — 65 mi5
  1. Stambaugh, MI 32 mi (52 km)
  2. Marquette (USW00094850), MI 58 mi (93 km)
  3. Oconto, WI 62 mi (100 km)
  4. Marquette (USW00014838), MI 62 mi (100 km)
  5. Washington Island, WI 65 mi (104 km)

Sources

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

Station coordinates: 45.7858, -88.0842.