U.S. Frost Dates by Weather Station

NOAA station USC00477708 · Wisconsin

Frost Dates for Shawano, WI

NOAA weather station Shawano 2 SSW (USC00477708), Wisconsin · elevation 806 ft (246 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 24only 1 spring in 10 still has a frost later
  • Typical last frostMay 950% chance of a frost after it
  • Typical first fall frostOctober 250% chance of a frost before it
  • Frost-free season144 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Shawano, WISpring: a frost after April 26 in 9 years out of 10, after May 9 in half of the years, after May 24 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before October 2 in half of the years, before October 15 in 9 years out of 10. Typical frost-free season: 144 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 9First frost ~Oct 2Frost season at Shawano, WISpring: a frost after April 26 in 9 years out of 10, after May 9 in half of the years, after May 24 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before October 2 in half of the years, before October 15 in 9 years out of 10. Typical frost-free season: 144 days.JFMAMJJASONDLast frost ~May 9First frost ~Oct 2
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)May 24September 18
50% (typical)May 9October 2
90% (likely)April 26October 15
Frost-free season (32°F, 50% chance)
144 days
Hard frost (28°F), last in spring, 50% chance after
April 30
Hard frost (28°F), first in fall, 50% chance before
October 13

The last 15 years (2006–2020 normals)

Typical last frost May 9 (same as the 30-year normal), typical first fall frost October 6 (4 days later). Frost-free season 148 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 Shawano: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 24, 20% May 19, 30% May 15, 40% May 12, 50% May 9, 60% May 6, 70% May 4, 80% April 30, 90% April 26. Observed last spring frost in recent years: 2021 May 29, 2022 May 5, 2023 May 3, 2024 April 26, 2025 May 9, 2026 May 14.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 24May 9Apr 262021: May 292022: May 52023: May 32024: April 262025: May 92026: May 14Fall at Shawano: chance of a frost before this dateFall, chance of a frost before the date: 10% September 18, 20% September 23, 30% September 27, 40% September 30, 50% October 2, 60% October 5, 70% October 7, 80% October 11, 90% October 15. Observed first fall frost in recent years: 2021 October 22, 2022 September 28, 2023 October 8, 2024 October 9, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 18Oct 2Oct 152021: October 222022: September 282023: October 82024: 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 5September 28
2023May 3October 8
2024April 26October 9
2025May 9October 8
2026May 14season not over yet

What these dates mean

The 144 days between the 50% dates in Shawano define the central window of even odds for a light frost, with the median spring date of May 9 and the median fall date of October 2. Around May 9 there is a 50 % chance that a 32°F frost will occur later in the season, and around October 2 there is a 50 % chance that a 32°F frost will have arrived earlier. These dates are not themselves frost events but mark the point where the likelihood splits.

For a cautious planting schedule, the spring light-frost date of May 24 carries only a 10 % chance of a frost later, making it the recommended day to set out tender crops, while the fall light-frost date of September 18 carries only a 10 % chance of a frost earlier, guiding the finish of tender harvests. The hard-frost median dates are April 30 in spring and October 13 in fall; a 28°F frost is more damaging because it reaches colder temperatures that can kill plant tissue that survives a 32°F light frost.

How to read the probabilities

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

  • Spring: "10% after May 24" 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 18" 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 Shawano, WINumbered nearest stations: 1 — Clintonville, WI — 12 mi; 2 — New London, WI — 28 mi; 3 — Rosholt, WI — 31 mi; 4 — Green Bay, WI — 31 mi; 5 — Oconto, WI — 34 mi.25 mi · 40 km1. Clintonville, WI — 12 mi12. New London, WI — 28 mi23. Rosholt, WI — 31 mi34. Green Bay, WI — 31 mi45. Oconto, WI — 34 mi5
  1. Clintonville, WI 12 mi (19 km)
  2. New London, WI 28 mi (46 km)
  3. Rosholt, WI 31 mi (50 km)
  4. Green Bay, WI 31 mi (50 km)
  5. Oconto, WI 34 mi (54 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: 44.7631, -88.6183.