U.S. Frost Dates by Weather Station

NOAA station USC00475164 · Wisconsin

Frost Dates for Mather, WI

NOAA weather station Mather 3 NW (USC00475164), Wisconsin · elevation 978 ft (298 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 20only 1 spring in 10 still has a frost later
  • Typical last frostMay 650% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season148 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Mather, WISpring: a frost after April 24 in 9 years out of 10, after May 6 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 3 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 148 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 6First frost ~Oct 3Frost season at Mather, WISpring: a frost after April 24 in 9 years out of 10, after May 6 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 3 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 148 days.JFMAMJJASONDLast frost ~May 6First frost ~Oct 3
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.Today

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 20September 19
50% (typical)May 6October 3
90% (likely)April 24October 16
Frost-free season (32°F, 50% chance)
148 days
Hard frost (28°F), last in spring, 50% chance after
April 26
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 5 (1 day earlier than the 30-year normal), typical first fall frost October 7 (4 days later). Frost-free season 154 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 Mather: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 20, 20% May 15, 30% May 12, 40% May 9, 50% May 6, 60% May 4, 70% May 1, 80% April 28, 90% April 24. Observed last spring frost in recent years: 2021 May 11, 2022 May 4, 2023 April 27, 2024 April 25, 2025 April 20, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 20May 6Apr 242021: May 112022: May 42023: April 272024: April 252025: April 202026: May 11Fall at Mather: chance of a frost before this dateFall, chance of a frost before the date: 10% September 19, 20% September 25, 30% September 29, 40% October 1, 50% October 3, 60% October 5, 70% October 8, 80% October 12, 90% October 16. Observed first fall frost in recent years: 2021 October 22, 2022 October 8, 2023 October 17, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 19Oct 3Oct 162021: October 222022: October 82023: October 172024: 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 11October 22
2022May 4October 8
2023April 27October 17
2024April 25October 16
2025April 20October 24
2026May 11season not over yet

What these dates mean

May 20 is the cautious spring date, with a 10% chance of a light frost later, and it lets a gardener set out tender crops after the risk of a damaging chill has become low. Planting before April 24 would be a gamble, since that date carries a 90% chance of a frost after it.

The 50% date is May 6, a median point where the odds of a light frost are even; it is not a frost date but marks the middle of the recorded range. In fall, September 19 is the cautious date, with only a 10% chance that a light frost has arrived earlier, providing a clear target for finishing the harvest of tender crops. The 50% date is October 3, again a median, even-odds point. The hard-frost median dates are April 26 in spring and October 15 in fall.

A hard frost at 28 °F can damage plant tissue that survives a light frost at 32 °F, making the hard-frost dates especially important for protecting crops.

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 19" 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 Mather, WINumbered nearest stations: 1 — Neillsville, WI — 27 mi; 2 — Sparta, WI — 28 mi; 3 — Mauston, WI — 30 mi; 4 — Marshfield, WI — 34 mi; 5 — Hancock Experiment Farm, WI — 40 mi.WIMN25 mi · 40 km1. Neillsville, WI — 27 mi12. Sparta, WI — 28 mi23. Mauston, WI — 30 mi34. Marshfield, WI — 34 mi45. Hancock Experiment Farm, WI — 40 mi5
  1. Neillsville, WI 27 mi (43 km)
  2. Sparta, WI 28 mi (46 km)
  3. Mauston, WI 30 mi (49 km)
  4. Marshfield, WI 34 mi (55 km)
  5. Hancock Experiment Farm, WI 40 mi (65 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: 44.1747, -90.3483.