U.S. Frost Dates by Weather Station

NOAA station USC00470175 · Wisconsin

Frost Dates for Amery, WI

NOAA weather station Amery (USC00470175), Wisconsin · elevation 1070 ft (326 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 21only 1 spring in 10 still has a frost later
  • Typical last frostMay 550% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season151 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Amery, WISpring: a frost after April 20 in 9 years out of 10, after May 5 in half of the years, after May 21 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 151 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 5First frost ~Oct 4Frost season at Amery, WISpring: a frost after April 20 in 9 years out of 10, after May 5 in half of the years, after May 21 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 151 days.JFMAMJJASONDLast frost ~May 5First 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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 21September 21
50% (typical)May 5October 4
90% (likely)April 20October 18
Frost-free season (32°F, 50% chance)
151 days
Hard frost (28°F), last in spring, 50% chance after
April 25
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 4 (1 day earlier than the 30-year normal), typical first fall frost October 7 (3 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 Amery: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 21, 20% May 15, 30% May 11, 40% May 8, 50% May 5, 60% May 2, 70% April 29, 80% April 26, 90% April 20. Observed last spring frost in recent years: 2021 May 11, 2022 April 29, 2023 May 3, 2024 April 25.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 21May 5Apr 202021: May 112022: April 292023: May 32024: April 25Fall at Amery: chance of a frost before this dateFall, chance of a frost before the date: 10% September 21, 20% September 26, 30% September 29, 40% October 1, 50% October 4, 60% October 7, 70% October 10, 80% October 13, 90% October 18. Observed first fall frost in recent years: 2021 October 22, 2022 September 28, 2023 October 28, 2024 October 14.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 21Oct 4Oct 182021: October 222022: September 282023: October 282024: October 14
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
2022April 29September 28
2023May 3October 28
2024April 25October 14
2025no datano data
2026no dataseason not over yet

What these dates mean

May 21 is the cautious spring date for Amery, carrying only a 10 % chance that a light frost will occur later, so a gardener can plan to set out tender crops with minimal risk. The median chance for a light frost in spring is the 50 % date of May 5, meaning there is an even odds of frost occurring after that point, while the 90 % chance date of April 20 makes an earlier planting a gamble.

In fall the 50 % date of October 4 marks the point where a light frost is equally likely to have arrived earlier or not, and the hard-frost 50 % dates are April 25 in spring and October 15 in fall; a hard frost can damage or kill plants that survive a light frost, making it the more critical threshold to watch. The cautious fall date is September 21, which carries only a 10 % chance that a light frost has arrived earlier, allowing a gardener to finish harvesting tender crops with confidence.

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 21" 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 Amery, WINumbered nearest stations: 1 — St. Croix Falls, WI — 16 mi; 2 — Luck, WI — 20 mi; 3 — Cumberland, WI — 23 mi; 4 — Ridgeland, WI — 24 mi; 5 — Wild River State Park, MN — 24 mi.WIMN25 mi · 40 km1. St. Croix Falls, WI — 16 mi12. Luck, WI — 20 mi23. Cumberland, WI — 23 mi34. Ridgeland, WI — 24 mi45. Wild River State Park, MN — 24 mi5
  1. St. Croix Falls, WI 16 mi (25 km)
  2. Luck, WI 20 mi (32 km)
  3. Cumberland, WI 23 mi (37 km)
  4. Ridgeland, WI 24 mi (38 km)
  5. Wild River State Park, MN 24 mi (39 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: 45.3011, -92.3631.