U.S. Frost Dates by Weather Station

NOAA station USW00014991 · Wisconsin

Frost Dates for Eau Claire, WI

NOAA weather station Eau Claire Regional Airport (USW00014991), Wisconsin · elevation 885 ft (270 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 21only 1 spring in 10 still has a frost later
  • Typical last frostMay 850% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season149 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Eau Claire, WISpring: a frost after April 24 in 9 years out of 10, after May 8 in half of the years, after May 21 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 4 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 149 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 8First frost ~Oct 4Frost season at Eau Claire, WISpring: a frost after April 24 in 9 years out of 10, after May 8 in half of the years, after May 21 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 4 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 149 days.JFMAMJJASONDLast frost ~May 8First frost ~Oct 4
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 21September 20
50% (typical)May 8October 4
90% (likely)April 24October 17
Frost-free season (32°F, 50% chance)
149 days
Hard frost (28°F), last in spring, 50% chance after
April 27
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 6 (2 days earlier than the 30-year normal), typical first fall frost October 7 (3 days later). Frost-free season 151 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 Eau Claire: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 21, 20% May 17, 30% May 13, 40% May 11, 50% May 8, 60% May 5, 70% May 2, 80% April 30, 90% April 24. Observed last spring frost in recent years: 2021 May 29, 2022 May 23, 2023 May 3, 2024 April 25, 2025 May 3, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 21May 8Apr 242021: May 292022: May 232023: May 32024: April 252025: May 32026: May 11Fall at Eau Claire: chance of a frost before this dateFall, chance of a frost before the date: 10% September 20, 20% September 25, 30% September 29, 40% October 1, 50% October 4, 60% October 7, 70% October 10, 80% October 12, 90% October 17. Observed first fall frost in recent years: 2021 October 21, 2022 September 28, 2023 October 17, 2024 October 15, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 20Oct 4Oct 172021: October 212022: September 282023: October 172024: October 152025: 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 29October 21
2022May 23September 28
2023May 3October 17
2024April 25October 15
2025May 3October 8
2026May 11season not over yet

What these dates mean

May 21 is the cautious spring date for Eau Claire, carrying only a 10 % chance of a light frost later; it marks the point at which a gardener can plan to set out tender crops with minimal frost risk.

The 50 % spring date, May 8, represents an even-odds moment, meaning there is a 50 % chance of a light frost later than this date. In the fall, the 50 % date is October 4, indicating a 50 % chance of a light frost earlier than that day. For a conservative schedule, the cautious fall date is September 20, when only a 10 % chance exists that a light frost has arrived, allowing the gardener to finish harvesting tender crops.

A hard frost at 28 °F can cause more severe damage to plants than 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 21" 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 20" 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 Eau Claire, WINumbered nearest stations: 1 — Bloomer, WI — 16 mi; 2 — Menomonie, WI — 22 mi; 3 — Mondovi, WI — 23 mi; 4 — Ridgeland, WI — 31 mi; 5 — Rice Lake, WI — 40 mi.MN25 mi · 40 km1. Bloomer, WI — 16 mi12. Menomonie, WI — 22 mi23. Mondovi, WI — 23 mi34. Ridgeland, WI — 31 mi45. Rice Lake, WI — 40 mi5
  1. Bloomer, WI 16 mi (25 km)
  2. Menomonie, WI 22 mi (35 km)
  3. Mondovi, WI 23 mi (37 km)
  4. Ridgeland, WI 31 mi (50 km)
  5. Rice Lake, 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: 44.8664, -91.4878.