U.S. Frost Dates by Weather Station

NOAA station USC00474195 · Wisconsin

Frost Dates for Kewaunee, WI

NOAA weather station Kewaunee (USC00474195), Wisconsin · elevation 593 ft (181 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 1850% chance of a frost before it
  • Frost-free season168 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Kewaunee, WISpring: a frost after April 16 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 October 2 in 1 year out of 10, before October 18 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 168 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 1First frost ~Oct 18Frost season at Kewaunee, WISpring: a frost after April 16 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 October 2 in 1 year out of 10, before October 18 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 168 days.JFMAMJJASONDLast frost ~May 1First frost ~Oct 18
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 17October 2
50% (typical)May 1October 18
90% (likely)April 16November 1
Frost-free season (32°F, 50% chance)
168 days
Hard frost (28°F), last in spring, 50% chance after
April 18
Hard frost (28°F), first in fall, 50% chance before
October 31

The last 15 years (2006–2020 normals)

Typical last frost April 30 (1 day earlier than the 30-year normal), typical first fall frost October 24 (6 days later). Frost-free season 176 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 Kewaunee: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 10, 30% May 6, 40% May 4, 50% May 1, 60% April 29, 70% April 25, 80% April 22, 90% April 16. Observed last spring frost in recent years: 2021 April 25, 2022 April 28, 2023 April 27, 2024 April 26, 2025 April 27.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 1Apr 162021: April 252022: April 282023: April 272024: April 262025: April 27Fall at Kewaunee: chance of a frost before this dateFall, chance of a frost before the date: 10% October 2, 20% October 7, 30% October 11, 40% October 15, 50% October 18, 60% October 21, 70% October 25, 80% October 29, 90% November 1. Observed first fall frost in recent years: 2021 November 2, 2022 October 15, 2023 October 30, 2024 November 2, 2025 October 25.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 2Oct 18Nov 12021: November 22022: October 152023: October 302024: November 22025: 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
2021April 25November 2
2022April 28October 15
2023April 27October 30
2024April 26November 2
2025April 27October 25
2026incomplete recordseason not over yet

What these dates mean

May 17 is the cautious spring date for light frosts in Kewaunee, offering gardeners a point at which there is only a 10 % chance of a frost later, so tender crops can be set out with relatively low risk. The median 50 % date, May 1, marks even odds for a light frost, while the 90 % chance date, April 16, is a gamble for early planting.

In the fall the cautious date is October 2, when there is just a 10 % chance that a light frost has already arrived, allowing growers to finish harvesting tender crops. October 18 serves as the 50 % median date, and November 1, with a 90 % chance of frost earlier, is a gamble. The 50 % hard-frost dates are April 18 in spring and October 31 in fall, each indicating an even likelihood of temperatures reaching 28 °F.

Hard frosts matter more because the lower 28 °F temperature can damage 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 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 October 2" 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 Kewaunee, WINumbered nearest stations: 1 — Two Rivers, WI — 22 mi; 2 — Manitowoc, WI — 27 mi; 3 — Green Bay, WI — 30 mi; 4 — Sturgeon Bay, WI — 30 mi; 5 — Oconto, WI — 37 mi.WIMI25 mi · 40 km1. Two Rivers, WI — 22 mi12. Manitowoc, WI — 27 mi23. Green Bay, WI — 30 mi34. Sturgeon Bay, WI — 30 mi45. Oconto, WI — 37 mi5
  1. Two Rivers, WI 22 mi (36 km)
  2. Manitowoc, WI 27 mi (43 km)
  3. Green Bay, WI 30 mi (48 km)
  4. Sturgeon Bay, WI 30 mi (48 km)
  5. Oconto, WI 37 mi (60 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: 44.4628, -87.505.