U.S. Frost Dates by Weather Station

NOAA station USC00477174 · Wisconsin

Frost Dates for Ridgeland, WI

NOAA weather station Ridgeland 1 NNE (USC00477174), Wisconsin · elevation 1080 ft (329 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 1050% chance of a frost after it
  • Typical first fall frostSeptember 2950% chance of a frost before it
  • Frost-free season140 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Ridgeland, WISpring: a frost after April 28 in 9 years out of 10, after May 10 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before September 29 in half of the years, before October 12 in 9 years out of 10. Typical frost-free season: 140 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 10First frost ~Sep 29Frost season at Ridgeland, WISpring: a frost after April 28 in 9 years out of 10, after May 10 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before September 29 in half of the years, before October 12 in 9 years out of 10. Typical frost-free season: 140 days.JFMAMJJASONDLast frost ~May 10First frost ~Sep 29
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 26September 13
50% (typical)May 10September 29
90% (likely)April 28October 12
Frost-free season (32°F, 50% chance)
140 days
Hard frost (28°F), last in spring, 50% chance after
April 30
Hard frost (28°F), first in fall, 50% chance before
October 9

The last 15 years (2006–2020 normals)

Typical last frost May 8 (2 days earlier than the 30-year normal), typical first fall frost October 3 (4 days later). Frost-free season 146 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 Ridgeland: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 20, 30% May 17, 40% May 13, 50% May 10, 60% May 8, 70% May 5, 80% May 2, 90% April 28. Observed last spring frost in recent years: 2021 May 12, 2022 May 4, 2023 May 3, 2024 May 10, 2025 April 30, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 10Apr 282021: May 122022: May 42023: May 32024: May 102025: April 302026: May 11Fall at Ridgeland: chance of a frost before this dateFall, chance of a frost before the date: 10% September 13, 20% September 18, 30% September 23, 40% September 26, 50% September 29, 60% October 1, 70% October 4, 80% October 8, 90% October 12. Observed first fall frost in recent years: 2021 October 22, 2022 September 28, 2023 October 9, 2024 October 4, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 13Sep 29Oct 122021: October 222022: September 282023: October 92024: October 42025: 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 12October 22
2022May 4September 28
2023May 3October 9
2024May 10October 4
2025April 30October 8
2026May 11season not over yet

What these dates mean

Setting out tender crops on the early spring date, April 28, is a gamble because there is a 90 % chance of a light frost after that day in Ridgeland. The cautious spring option is the later May 26 date, when only a 10 % chance of frost remains.

The 50 % dates mark the point of even odds: the median light-frost date in spring is May 10, and the median in fall is September 29. A gardener who follows a cautious plan would finish harvesting tender crops by the fall September 13 date, which carries a 10 % chance of a frost earlier than that day. The hard-frost 50 % dates are April 30 in spring and October 9 in fall; a hard frost matters more than a light frost because the lower temperature of 28 °F can damage plants that survive a 32 °F event.

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 13" 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 Ridgeland, WINumbered nearest stations: 1 — Rice Lake, WI — 15 mi; 2 — Bloomer, WI — 21 mi; 3 — Cumberland, WI — 23 mi; 4 — Menomonie, WI — 24 mi; 5 — Amery, WI — 24 mi.MN25 mi · 40 km1. Rice Lake, WI — 15 mi12. Bloomer, WI — 21 mi23. Cumberland, WI — 23 mi34. Menomonie, WI — 24 mi45. Amery, WI — 24 mi5
  1. Rice Lake, WI 15 mi (24 km)
  2. Bloomer, WI 21 mi (34 km)
  3. Cumberland, WI 23 mi (37 km)
  4. Menomonie, WI 24 mi (38 km)
  5. Amery, WI 24 mi (38 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: 45.2142, -91.8875.