U.S. Frost Dates by Weather Station

NOAA station USC00474953 · Wisconsin

Frost Dates for Madeline Island, WI

NOAA weather station Madeline Island (USC00474953), Wisconsin · elevation 660 ft (201 m) · hardiness zone 5a*

  • Lower-risk planting dateafter June 3only 1 spring in 10 still has a frost later
  • Typical last frostMay 2050% chance of a frost after it
  • Typical first fall frostOctober 950% chance of a frost before it
  • Frost-free season140 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Madeline Island, WISpring: a frost after May 5 in 9 years out of 10, after May 20 in half of the years, after June 3 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 9 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 140 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 20First frost ~Oct 9Frost season at Madeline Island, WISpring: a frost after May 5 in 9 years out of 10, after May 20 in half of the years, after June 3 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 9 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 140 days.JFMAMJJASONDLast frost ~May 20First frost ~Oct 9
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 3September 25
50% (typical)May 20October 9
90% (likely)May 5October 23
Frost-free season (32°F, 50% chance)
140 days
Hard frost (28°F), last in spring, 50% chance after
May 6
Hard frost (28°F), first in fall, 50% chance before
October 23

The last 15 years (2006–2020 normals)

Typical last frost May 19 (1 day earlier than the 30-year normal), typical first fall frost October 12 (3 days later). Frost-free season 145 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 Madeline Island: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 3, 20% May 30, 30% May 26, 40% May 23, 50% May 20, 60% May 17, 70% May 14, 80% May 10, 90% May 5.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 3May 20May 5Fall at Madeline Island: chance of a frost before this dateFall, chance of a frost before the date: 10% September 25, 20% October 1, 30% October 4, 40% October 6, 50% October 9, 60% October 12, 70% October 15, 80% October 19, 90% October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 25Oct 9Oct 23
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.

What these dates mean

June 3 marks the cautious spring light-frost date for Madeline Island; with only a 10 % chance of a frost later, a gardener can plan to set out tender crops after that day with minimal risk. The 50 % date is May 20, indicating an even odds chance of a frost later than this date, while the earlier May 5 date carries a 90 % chance and is a gamble for tender crops. In the fall, September 25 is the cautious light-frost date, offering only a 10 % chance that a frost has arrived earlier, so harvesting tender crops can be scheduled up to that point. The 50 % date is October 9, meaning a 50 % chance of a frost earlier than this date, and the later October 23 date bears a 90 % chance and is a gamble. A hard frost at 28 °F, represented by the 50 % dates May 6 and October 23, can injure plants more severely than a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after June 3" 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 25" 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 Madeline Island, WINumbered nearest stations: 1 — Hurley, WI — 35 mi; 2 — Ironwood, MI — 35 mi; 3 — Two Harbors, MN — 46 mi; 4 — Wolf Ridge Elc, MN — 51 mi; 5 — Bergland Dam, MI — 59 mi.WIMIMN25 mi · 40 km1. Hurley, WI — 35 mi12. Ironwood, MI — 35 mi23. Two Harbors, MN — 46 mi34. Wolf Ridge Elc, MN — 51 mi45. Bergland Dam, MI — 59 mi5
  1. Hurley, WI 35 mi (56 km)
  2. Ironwood, MI 35 mi (56 km)
  3. Two Harbors, MN 46 mi (74 km)
  4. Wolf Ridge Elc, MN 51 mi (82 km)
  5. Bergland Dam, MI 59 mi (95 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: 46.7781, -90.7653.