U.S. Frost Dates by Weather Station

NOAA station USC00475017 · Wisconsin

Frost Dates for Manitowoc, WI

NOAA weather station Manitowoc (USC00475017), Wisconsin · elevation 584 ft (178 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 15only 1 spring in 10 still has a frost later
  • Typical last frostApril 3050% chance of a frost after it
  • Typical first fall frostOctober 2050% chance of a frost before it
  • Frost-free season171 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Manitowoc, WISpring: a frost after April 14 in 9 years out of 10, after April 30 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 20 in half of the years, before November 3 in 9 years out of 10. Typical frost-free season: 171 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 30First frost ~Oct 20Frost season at Manitowoc, WISpring: a frost after April 14 in 9 years out of 10, after April 30 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 20 in half of the years, before November 3 in 9 years out of 10. Typical frost-free season: 171 days.JFMAMJJASONDLast frost ~Apr 30First frost ~Oct 20
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 15October 3
50% (typical)April 30October 20
90% (likely)April 14November 3
Frost-free season (32°F, 50% chance)
171 days
Hard frost (28°F), last in spring, 50% chance after
April 16
Hard frost (28°F), first in fall, 50% chance before
November 1

The last 15 years (2006–2020 normals)

Typical last frost April 26 (4 days earlier than the 30-year normal), typical first fall frost October 26 (6 days later). Frost-free season 180 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 Manitowoc: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 15, 20% May 10, 30% May 6, 40% May 2, 50% April 30, 60% April 26, 70% April 23, 80% April 19, 90% April 14. Observed last spring frost in recent years: 2021 April 25, 2022 April 28, 2023 April 26, 2024 April 25, 2025 April 10, 2026 May 2.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 15Apr 30Apr 142021: April 252022: April 282023: April 262024: April 252025: April 102026: May 2Fall at Manitowoc: chance of a frost before this dateFall, chance of a frost before the date: 10% October 3, 20% October 8, 30% October 13, 40% October 17, 50% October 20, 60% October 23, 70% October 27, 80% October 30, 90% November 3. Observed first fall frost in recent years: 2021 November 2, 2022 October 8, 2023 October 30, 2024 November 2, 2025 November 2.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 3Oct 20Nov 32021: November 22022: October 82023: October 302024: November 22025: November 2
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 8
2023April 26October 30
2024April 25November 2
2025April 10November 2
2026May 2season not over yet

What these dates mean

The 171 days between the 50% dates in Manitowoc—April 30 and October 20—represent the period in which a light frost (32 °F) is statistically as likely as not to occur. Within this span gardeners can expect a lower overall risk of light frost, while outside it the chance rises sharply.

A cautious spring planting plan uses the May 15 date, which carries a 10 % chance that a light frost will still occur later; planting earlier on April 14 bears a 90 % chance of a later frost and is a gamble. In the fall, the cautious finish date is October 3, with only a 10 % chance that a light frost has already arrived, whereas extending to November 3 carries a 90 % chance of an earlier frost. The median hard-frost dates are April 16 and November 1. A hard frost at 28 °F can damage plant tissue that would survive 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 May 15" 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 3" 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 Manitowoc, WINumbered nearest stations: 1 — Two Rivers, WI — 6 mi; 2 — Chilton, WI — 25 mi; 3 — Kewaunee, WI — 27 mi; 4 — Plymouth, WI — 29 mi; 5 — Green Bay, WI — 36 mi.WIMI25 mi · 40 km1. Two Rivers, WI — 6 mi12. Chilton, WI — 25 mi23. Kewaunee, WI — 27 mi34. Plymouth, WI — 29 mi45. Green Bay, WI — 36 mi5
  1. Two Rivers, WI 6 mi (9 km)
  2. Chilton, WI 25 mi (40 km)
  3. Kewaunee, WI 27 mi (43 km)
  4. Plymouth, WI 29 mi (47 km)
  5. Green Bay, WI 36 mi (59 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: 44.0869, -87.6522.