U.S. Frost Dates by Weather Station

NOAA station USC00475120 · Wisconsin

Frost Dates for Marshfield, WI

NOAA weather station Marshfield Experiment Farm (USC00475120), Wisconsin · elevation 1237 ft (377 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 20only 1 spring in 10 still has a frost later
  • Typical last frostMay 550% chance of a frost after it
  • Typical first fall frostOctober 550% chance of a frost before it
  • Frost-free season150 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Marshfield, WISpring: a frost after April 22 in 9 years out of 10, after May 5 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 5 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 150 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 5First frost ~Oct 5Frost season at Marshfield, WISpring: a frost after April 22 in 9 years out of 10, after May 5 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 5 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 150 days.JFMAMJJASONDLast frost ~May 5First frost ~Oct 5
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 20September 22
50% (typical)May 5October 5
90% (likely)April 22October 19
Frost-free season (32°F, 50% chance)
150 days
Hard frost (28°F), last in spring, 50% chance after
April 25
Hard frost (28°F), first in fall, 50% chance before
October 16

The last 15 years (2006–2020 normals)

Typical last frost May 2 (3 days earlier than the 30-year normal), typical first fall frost October 10 (5 days later). Frost-free season 159 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 Marshfield: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 20, 20% May 15, 30% May 11, 40% May 8, 50% May 5, 60% May 3, 70% April 30, 80% April 26, 90% April 22. Observed last spring frost in recent years: 2021 May 28, 2022 May 4, 2023 April 30, 2024 April 25, 2025 April 17, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 20May 5Apr 222021: May 282022: May 42023: April 302024: April 252025: April 172026: May 11Fall at Marshfield: chance of a frost before this dateFall, chance of a frost before the date: 10% September 22, 20% September 26, 30% September 30, 40% October 2, 50% October 5, 60% October 8, 70% October 10, 80% October 14, 90% October 19. Observed first fall frost in recent years: 2021 October 22, 2022 September 28, 2023 October 22, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 22Oct 5Oct 192021: October 222022: September 282023: October 222024: October 162025: 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
2021May 28October 22
2022May 4September 28
2023April 30October 22
2024April 25October 16
2025April 17October 24
2026May 11season not over yet

What these dates mean

September 22 is the cautious date to finish harvesting tender crops, with only a 10% chance a light frost has arrived earlier.

The 50% light-frost dates are May 5 in spring and October 5 in fall; a gardener has an even chance of a frost occurring after the spring median or before the fall median. The 50% hard-frost dates are April 25 and October 16; these generally clearly mark the points where a hard frost is as likely as not.

For a cautious plan, tender crops are set out after the spring cautious date of May 20 and are harvested before the fall cautious date of September 22. A hard frost at 28°F can damage or kill 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 20" 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 Marshfield, WINumbered nearest stations: 1 — Neillsville, WI — 21 mi; 2 — Stevens Point, WI — 28 mi; 3 — near Wausau, WI — 32 mi; 4 — Mather, WI — 34 mi; 5 — Medford, WI — 35 mi.25 mi · 40 km1. Neillsville, WI — 21 mi12. Stevens Point, WI — 28 mi23. near Wausau, WI — 32 mi34. Mather, WI — 34 mi45. Medford, WI — 35 mi5
  1. Neillsville, WI 21 mi (34 km)
  2. Stevens Point, WI 28 mi (46 km)
  3. near Wausau, WI 32 mi (51 km)
  4. Mather, WI 34 mi (55 km)
  5. Medford, WI 35 mi (57 km)

Sources

* Hardiness zone 4b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 44.6411, -90.1333.