U.S. Frost Dates by Weather Station

NOAA station USC00472839 · Wisconsin

Frost Dates for Fond du Lac, WI

NOAA weather station Fond Du Lac WWTP (USC00472839), Wisconsin · elevation 750 ft (229 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 150% chance of a frost after it
  • Typical first fall frostOctober 1250% chance of a frost before it
  • Frost-free season162 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Fond du Lac, WISpring: a frost after April 18 in 9 years out of 10, after May 1 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 12 in half of the years, before October 25 in 9 years out of 10. Typical frost-free season: 162 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 1First frost ~Oct 12Frost season at Fond du Lac, WISpring: a frost after April 18 in 9 years out of 10, after May 1 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 12 in half of the years, before October 25 in 9 years out of 10. Typical frost-free season: 162 days.JFMAMJJASONDLast frost ~May 1First 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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 17September 28
50% (typical)May 1October 12
90% (likely)April 18October 25
Frost-free season (32°F, 50% chance)
162 days
Hard frost (28°F), last in spring, 50% chance after
April 20
Hard frost (28°F), first in fall, 50% chance before
October 24

The last 15 years (2006–2020 normals)

Typical last frost May 1 (same as the 30-year normal), typical first fall frost October 16 (4 days later). Frost-free season 168 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 Fond du Lac: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 12, 30% May 8, 40% May 5, 50% May 1, 60% April 29, 70% April 26, 80% April 22, 90% April 18. Observed last spring frost in recent years: 2021 April 25, 2022 April 28, 2023 May 2, 2024 April 25, 2025 April 16, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 1Apr 182021: April 252022: April 282023: May 22024: April 252025: April 162026: May 7Fall at Fond du Lac: chance of a frost before this dateFall, chance of a frost before the date: 10% September 28, 20% October 2, 30% October 6, 40% October 9, 50% October 12, 60% October 15, 70% October 17, 80% October 21, 90% October 25. Observed first fall frost in recent years: 2021 October 24, 2022 October 8, 2023 October 30, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 28Oct 12Oct 252021: October 242022: October 82023: October 302025: October 24
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
2021April 25October 24
2022April 28October 8
2023May 2October 30
2024April 25incomplete record
2025April 16October 24
2026May 7season not over yet

What these dates mean

May 17 is the cautious spring date for Fond du Lac, allowing a gardener to set out tender crops when the chance of a later light frost is only 10%. The median point for light-frost risk is May 1, which carries a 50% chance of a frost later than this date, while the median hard-frost point is April 20. In the fall, September 28 serves as the cautious date to finish harvesting tender crops, with just a 10% chance that a light frost has arrived earlier. The 50% light-frost date is October 12, representing an even odds of a frost earlier than this date, and the hard-frost median is October 24.

A hard frost at 28 °F is more critical than a light frost at 32 °F because the colder temperature can cause far greater damage to plant tissue.

How to read the probabilities

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

  • Spring: "10% after May 17" 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 28" 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 Fond du Lac, WINumbered nearest stations: 1 — Oshkosh, WI — 16 mi; 2 — Chilton, WI — 22 mi; 3 — Plymouth, WI — 24 mi; 4 — Horicon, WI — 26 mi; 5 — Beaver Dam, WI — 31 mi.WI25 mi · 40 km1. Oshkosh, WI — 16 mi12. Chilton, WI — 22 mi23. Plymouth, WI — 24 mi34. Horicon, WI — 26 mi45. Beaver Dam, WI — 31 mi5
  1. Oshkosh, WI 16 mi (26 km)
  2. Chilton, WI 22 mi (36 km)
  3. Plymouth, WI 24 mi (39 km)
  4. Horicon, WI 26 mi (42 km)
  5. Beaver Dam, WI 31 mi (50 km)

Sources

* Hardiness zone 5b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 43.7953, -88.4533.