U.S. Frost Dates by Weather Station

NOAA station USC00475255 · Wisconsin

Frost Dates for Medford, WI

NOAA weather station Medford (USC00475255), Wisconsin · elevation 1470 ft (448 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 1150% chance of a frost after it
  • Typical first fall frostOctober 150% chance of a frost before it
  • Frost-free season141 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Medford, WISpring: a frost after April 29 in 9 years out of 10, after May 11 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before October 1 in half of the years, before October 13 in 9 years out of 10. Typical frost-free season: 141 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 11First frost ~Oct 1Frost season at Medford, WISpring: a frost after April 29 in 9 years out of 10, after May 11 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before October 1 in half of the years, before October 13 in 9 years out of 10. Typical frost-free season: 141 days.JFMAMJJASONDLast frost ~May 11First frost ~Oct 1
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 26September 17
50% (typical)May 11October 1
90% (likely)April 29October 13
Frost-free season (32°F, 50% chance)
141 days
Hard frost (28°F), last in spring, 50% chance after
May 1
Hard frost (28°F), first in fall, 50% chance before
October 11

The last 15 years (2006–2020 normals)

Typical last frost May 9 (2 days earlier than the 30-year normal), typical first fall frost October 3 (2 days later). Frost-free season 145 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 Medford: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 21, 30% May 18, 40% May 14, 50% May 11, 60% May 8, 70% May 5, 80% May 3, 90% April 29. Observed last spring frost in recent years: 2021 May 29, 2022 May 23, 2023 May 3.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 11Apr 292021: May 292022: May 232023: May 3Fall at Medford: chance of a frost before this dateFall, chance of a frost before the date: 10% September 17, 20% September 22, 30% September 26, 40% September 28, 50% October 1, 60% October 4, 70% October 6, 80% October 9, 90% October 13. Observed first fall frost in recent years: 2021 October 22, 2022 September 28, 2023 October 17.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 17Oct 1Oct 132021: October 222022: September 282023: October 17
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 29October 22
2022May 23September 28
2023May 3October 17
2024no dataincomplete record
2025incomplete recordincomplete record
2026no dataseason not over yet

What these dates mean

September 17 marks the cautious fall date for Medford, Wisconsin, indicating only a 10 % chance that a light frost has arrived and signaling the latest reliable day to finish harvesting tender crops.

The 50 % light-frost dates are May 11 in spring and October 1 in fall; these dates are not frost dates but give a gardener an even chance of a frost occurring later (spring) or earlier (fall). The median hard-frost dates are May 1 and October 11, and a hard frost can damage plants more severely than a light frost because it reaches a lower temperature.

For a cautious plan, tender crops should be set out no earlier than May 26, when the chance of a later light frost is only 10 %, and should be harvested by September 17, the cautious fall date with a similarly low frost risk.

How to read the probabilities

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

  • Spring: "10% after May 26" 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 17" 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 Medford, WINumbered nearest stations: 1 — Merrill, WI — 33 mi; 2 — Marshfield, WI — 35 mi; 3 — near Wausau, WI — 38 mi; 4 — Neillsville, WI — 42 mi; 5 — Bloomer, WI — 56 mi.WI25 mi · 40 km1. Merrill, WI — 33 mi12. Marshfield, WI — 35 mi23. near Wausau, WI — 38 mi34. Neillsville, WI — 42 mi45. Bloomer, WI — 56 mi5
  1. Merrill, WI 33 mi (54 km)
  2. Marshfield, WI 35 mi (57 km)
  3. near Wausau, WI 38 mi (61 km)
  4. Neillsville, WI 42 mi (68 km)
  5. Bloomer, WI 56 mi (90 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: 45.1308, -90.3439.