U.S. Frost Dates by Weather Station

NOAA station USC00476208 · Wisconsin

Frost Dates for Oconto, WI

NOAA weather station Oconto 4 W (USC00476208), Wisconsin · elevation 660 ft (201 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 23only 1 spring in 10 still has a frost later
  • Typical last frostMay 950% chance of a frost after it
  • Typical first fall frostOctober 650% chance of a frost before it
  • Frost-free season150 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Oconto, WISpring: a frost after April 25 in 9 years out of 10, after May 9 in half of the years, after May 23 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 6 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 150 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 9First frost ~Oct 6Frost season at Oconto, WISpring: a frost after April 25 in 9 years out of 10, after May 9 in half of the years, after May 23 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 6 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 150 days.JFMAMJJASONDLast frost ~May 9First frost ~Oct 6
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 23September 22
50% (typical)May 9October 6
90% (likely)April 25October 19
Frost-free season (32°F, 50% chance)
150 days
Hard frost (28°F), last in spring, 50% chance after
April 28
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost May 7 (2 days earlier than the 30-year normal), typical first fall frost October 11 (5 days later). Frost-free season 155 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 Oconto: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 23, 20% May 18, 30% May 15, 40% May 12, 50% May 9, 60% May 7, 70% May 3, 80% April 30, 90% April 25. Observed last spring frost in recent years: 2021 May 13, 2022 May 6, 2023 May 26, 2024 April 26, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 23May 9Apr 252021: May 132022: May 62023: May 262024: April 262026: May 11Fall at Oconto: chance of a frost before this dateFall, chance of a frost before the date: 10% September 22, 20% September 27, 30% October 1, 40% October 3, 50% October 6, 60% October 8, 70% October 12, 80% October 15, 90% October 19. Observed first fall frost in recent years: 2021 October 23, 2022 September 23, 2023 October 8, 2024 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 22Oct 6Oct 192021: October 232022: September 232023: October 82024: 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 13October 23
2022May 6September 23
2023May 26October 8
2024April 26October 8
2025no dataincomplete record
2026May 11season not over yet

What these dates mean

The 150 days between the 32°F 50% dates, May 9 and October 6, frame the span when temperatures are more likely to stay above the light-frost threshold for tender crops. For a gardener in Oconto the 50% date means an even chance of a light frost: there is a 50% chance of a frost later than May 9 in spring and a 50% chance of a frost earlier than October 6 in fall.

A cautious spring schedule uses the May 23 date, which carries only a 10% chance of a frost later, while a cautious fall schedule relies on September 22, which has only a 10% chance of a frost earlier. Planting or harvesting around those dates reduces the likelihood of a damaging light frost.

Hard frost at 28°F, with median dates of April 28 and October 17, is more destructive than a light frost at 32°F because it can kill plants that would survive the milder temperature.

How to read the probabilities

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

  • Spring: "10% after May 23" 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 22" 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 Oconto, WINumbered nearest stations: 1 — Green Bay, WI — 28 mi; 2 — Sturgeon Bay, WI — 30 mi; 3 — Shawano, WI — 34 mi; 4 — Kewaunee, WI — 37 mi; 5 — Clintonville, WI — 43 mi.WI25 mi · 40 km1. Green Bay, WI — 28 mi12. Sturgeon Bay, WI — 30 mi23. Shawano, WI — 34 mi34. Kewaunee, WI — 37 mi45. Clintonville, WI — 43 mi5
  1. Green Bay, WI 28 mi (45 km)
  2. Sturgeon Bay, WI 30 mi (49 km)
  3. Shawano, WI 34 mi (54 km)
  4. Kewaunee, WI 37 mi (60 km)
  5. Clintonville, WI 43 mi (69 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: 44.8919, -87.955.