U.S. Frost Dates by Weather Station

NOAA station USC00470308 · Wisconsin

Frost Dates for Arlington, WI

NOAA weather station Arlington (USC00470308), Wisconsin · elevation 1052 ft (321 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 18only 1 spring in 10 still has a frost later
  • Typical last frostMay 450% chance of a frost after it
  • Typical first fall frostOctober 650% chance of a frost before it
  • Frost-free season154 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Arlington, WISpring: a frost after April 20 in 9 years out of 10, after May 4 in half of the years, after May 18 in 1 year out of 10. Fall: the first frost comes before September 23 in 1 year out of 10, before October 6 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 154 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 4First frost ~Oct 6Frost season at Arlington, WISpring: a frost after April 20 in 9 years out of 10, after May 4 in half of the years, after May 18 in 1 year out of 10. Fall: the first frost comes before September 23 in 1 year out of 10, before October 6 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 154 days.JFMAMJJASONDLast frost ~May 4First frost ~Oct 6
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 18September 23
50% (typical)May 4October 6
90% (likely)April 20October 20
Frost-free season (32°F, 50% chance)
154 days
Hard frost (28°F), last in spring, 50% chance after
April 22
Hard frost (28°F), first in fall, 50% chance before
October 18

The last 15 years (2006–2020 normals)

Typical last frost May 3 (1 day earlier than the 30-year normal), typical first fall frost October 11 (5 days later). Frost-free season 160 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 Arlington: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 18, 20% May 14, 30% May 10, 40% May 6, 50% May 4, 60% May 1, 70% April 28, 80% April 24, 90% April 20. Observed last spring frost in recent years: 2021 May 30, 2022 May 4, 2023 May 3, 2024 April 26, 2025 May 9, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 18May 4Apr 202021: May 302022: May 42023: May 32024: April 262025: May 92026: May 11Fall at Arlington: chance of a frost before this dateFall, chance of a frost before the date: 10% September 23, 20% September 28, 30% October 1, 40% October 4, 50% October 6, 60% October 9, 70% October 12, 80% October 15, 90% October 20. Observed first fall frost in recent years: 2021 October 22, 2022 September 29, 2023 October 9, 2024 October 15, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 23Oct 6Oct 202021: October 222022: September 292023: October 92024: October 152025: 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 30October 22
2022May 4September 29
2023May 3October 9
2024April 26October 15
2025May 9October 24
2026May 11season not over yet

What these dates mean

September 23 is the cautious fall date for finishing the harvest of tender crops, carrying only a 10 % chance that a light frost has arrived earlier.

In spring the cautious date for setting out tender crops is May 18, when there is only a 10 % chance of a light frost later; the 50 % light-frost date is May 4, at which point there is a 50 % chance of a frost later. In fall the cautious date to end harvesting tender crops is September 23, with a 10 % chance of a frost earlier, and the 50 % light-frost date is October 6, when there is a 50 % chance of a frost earlier.

The 50 % hard-frost dates are April 22 in spring and October 18 in fall; a hard frost at 28 °F can damage plant tissue that would survive a light frost at 32 °F, making it a more critical threshold for gardeners.

How to read the probabilities

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

  • Spring: "10% after May 18" 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 23" 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 Arlington, WINumbered nearest stations: 1 — Madison (Madison-Dane Airport), WI — 11 mi; 2 — Portage, WI — 16 mi; 3 — Charmany Farm, WI — 18 mi; 4 — UW Arboretum - Madison, WI — 19 mi; 5 — Beaver Dam, WI — 27 mi.IL25 mi · 40 km1. Madison (Madison-Dane Airport), WI — 11 mi12. Portage, WI — 16 mi23. Charmany Farm, WI — 18 mi34. UW Arboretum - Madison, WI — 19 mi45. Beaver Dam, WI — 27 mi5
  1. Madison (Madison-Dane Airport), WI 11 mi (18 km)
  2. Portage, WI 16 mi (26 km)
  3. Charmany Farm, WI 18 mi (29 km)
  4. UW Arboretum - Madison, WI 19 mi (30 km)
  5. Beaver Dam, WI 27 mi (43 km)

Sources

* Hardiness zone 5a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 43.3042, -89.3453.