U.S. Frost Dates by Weather Station

NOAA station USC00478672 · Wisconsin

Frost Dates for Two Rivers, WI

NOAA weather station Two Rivers (USC00478672), Wisconsin · elevation 589 ft (180 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 10only 1 spring in 10 still has a frost later
  • Typical last frostApril 2750% chance of a frost after it
  • Typical first fall frostOctober 2150% chance of a frost before it
  • Frost-free season175 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Two Rivers, WISpring: a frost after April 14 in 9 years out of 10, after April 27 in half of the years, after May 10 in 1 year out of 10. Fall: the first frost comes before October 4 in 1 year out of 10, before October 21 in half of the years, before November 3 in 9 years out of 10. Typical frost-free season: 175 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 27First frost ~Oct 21Frost season at Two Rivers, WISpring: a frost after April 14 in 9 years out of 10, after April 27 in half of the years, after May 10 in 1 year out of 10. Fall: the first frost comes before October 4 in 1 year out of 10, before October 21 in half of the years, before November 3 in 9 years out of 10. Typical frost-free season: 175 days.JFMAMJJASONDLast frost ~Apr 27First frost ~Oct 21
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 10October 4
50% (typical)April 27October 21
90% (likely)April 14November 3
Frost-free season (32°F, 50% chance)
175 days
Hard frost (28°F), last in spring, 50% chance after
April 14
Hard frost (28°F), first in fall, 50% chance before
November 1

The last 15 years (2006–2020 normals)

Typical last frost April 28 (1 day later than the 30-year normal), typical first fall frost October 26 (5 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 Two Rivers: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 10, 20% May 5, 30% May 2, 40% April 30, 50% April 27, 60% April 24, 70% April 21, 80% April 17, 90% April 14. Observed last spring frost in recent years: 2021 April 25, 2022 April 28, 2023 April 26, 2024 April 25, 2025 April 12, 2026 May 2.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 10Apr 27Apr 142021: April 252022: April 282023: April 262024: April 252025: April 122026: May 2Fall at Two Rivers: chance of a frost before this dateFall, chance of a frost before the date: 10% October 4, 20% October 9, 30% October 13, 40% October 17, 50% October 21, 60% October 24, 70% October 27, 80% October 31, 90% November 3. Observed first fall frost in recent years: 2021 November 2, 2022 October 15, 2023 October 30, 2024 November 2, 2025 November 2.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 4Oct 21Nov 32021: November 22022: October 152023: 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 15
2023April 26October 30
2024April 25November 2
2025April 12November 2
2026May 2season not over yet

What these dates mean

The 175 days between the 32 °F 50 % dates of April 27 and October 21 frame the period when tender crops can be grown in Two Rivers. Within that span, light frosts become increasingly unlikely after the cautious spring date and increasingly likely before the cautious fall date.

For a gardener, the 50 % dates are reference points of even odds for a light frost; they are not frost dates themselves. The cautious date for setting out tender crops in spring is May 10, when there is only a 10 % chance of a later frost, while April 14 carries a 90 % chance and is a gamble. In fall, the cautious date to finish harvesting tender crops is October 4, with a 10 % chance of an earlier frost, whereas November 3 has a 90 % chance and is a gamble. The 50 % hard-frost dates are April 14 and November 1; a hard frost at 28 °F can damage plants that survive a light frost at 32 °F, so it represents a greater threat.

How to read the probabilities

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

  • Spring: "10% after May 10" 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 4" 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 Two Rivers, WINumbered nearest stations: 1 — Manitowoc, WI — 6 mi; 2 — Kewaunee, WI — 22 mi; 3 — Chilton, WI — 30 mi; 4 — Plymouth, WI — 35 mi; 5 — Green Bay, WI — 36 mi.WIMI25 mi · 40 km1. Manitowoc, WI — 6 mi12. Kewaunee, WI — 22 mi23. Chilton, WI — 30 mi34. Plymouth, WI — 35 mi45. Green Bay, WI — 36 mi5
  1. Manitowoc, WI 6 mi (9 km)
  2. Kewaunee, WI 22 mi (36 km)
  3. Chilton, WI 30 mi (48 km)
  4. Plymouth, WI 35 mi (56 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: 44.1431, -87.5678.