U.S. Frost Dates by Weather Station

NOAA station USC00471205 · Wisconsin

Frost Dates for Burlington, WI

NOAA weather station Burlington (USC00471205), Wisconsin · elevation 751 ft (229 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 23only 1 spring in 10 still has a frost later
  • Typical last frostMay 550% chance of a frost after it
  • Typical first fall frostOctober 950% chance of a frost before it
  • Frost-free season156 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Burlington, WISpring: a frost after April 21 in 9 years out of 10, after May 5 in half of the years, after May 23 in 1 year out of 10. Fall: the first frost comes before September 24 in 1 year out of 10, before October 9 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 156 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 5First frost ~Oct 9Frost season at Burlington, WISpring: a frost after April 21 in 9 years out of 10, after May 5 in half of the years, after May 23 in 1 year out of 10. Fall: the first frost comes before September 24 in 1 year out of 10, before October 9 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 156 days.JFMAMJJASONDLast frost ~May 5First frost ~Oct 9
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 23September 24
50% (typical)May 5October 9
90% (likely)April 21October 24
Frost-free season (32°F, 50% chance)
156 days
Hard frost (28°F), last in spring, 50% chance after
April 24
Hard frost (28°F), first in fall, 50% chance before
October 22

The last 15 years (2006–2020 normals)

Typical last frost May 2 (3 days earlier than the 30-year normal), typical first fall frost October 14 (5 days later). Frost-free season 162 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 Burlington: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 23, 20% May 16, 30% May 11, 40% May 8, 50% May 5, 60% May 2, 70% April 30, 80% April 26, 90% April 21. Observed last spring frost in recent years: 2021 May 31, 2022 April 28, 2023 May 18, 2024 April 26, 2025 May 10, 2026 May 12.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 23May 5Apr 212021: May 312022: April 282023: May 182024: April 262025: May 102026: May 12Fall at Burlington: chance of a frost before this dateFall, chance of a frost before the date: 10% September 24, 20% September 30, 30% October 2, 40% October 6, 50% October 9, 60% October 12, 70% October 15, 80% October 19, 90% October 24. 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 1Nov 1Sep 24Oct 9Oct 242021: 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 31October 22
2022April 28October 8
2023May 18October 17
2024April 26October 16
2025May 10October 24
2026May 12season not over yet

What these dates mean

The 156 days between the 50% dates in Burlington, Wisconsin, mark the span in which the average daily temperature normally remains above the light-frost threshold of 32°F. The 50% spring date is May 5, when there is an even chance of a light frost occurring later, and the 50% fall date is October 9, when there is an even chance of a light frost occurring earlier.

The cautious spring date for setting out tender crops is May 23, which carries only a 10 % chance that a light frost will follow. The cautious fall date for finishing harvest of tender crops is September 24, with only a 10 % chance that a light frost has already arrived. By contrast, April 21 in spring and October 24 in fall each hold a 90 % chance of a light frost, representing a gamble for tender plants.

A hard frost at 28°F can injure plant tissue that would survive a light frost at 32°F, so the hard-frost risk is more critical.

How to read the probabilities

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

  • Spring: "10% after May 23" 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 24" 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 Burlington, WINumbered nearest stations: 1 — Kenosha, WI — 23 mi; 2 — near McHenry, IL — 24 mi; 3 — Racine, WI — 24 mi; 4 — near Milwaukee, WI — 28 mi; 5 — Whitewater, WI — 28 mi.IL25 mi · 40 km1. Kenosha, WI — 23 mi12. near McHenry, IL — 24 mi23. Racine, WI — 24 mi34. near Milwaukee, WI — 28 mi45. Whitewater, WI — 28 mi5
  1. Kenosha, WI 23 mi (37 km)
  2. near McHenry, IL 24 mi (38 km)
  3. Racine, WI 24 mi (39 km)
  4. near Milwaukee, WI 28 mi (44 km)
  5. Whitewater, WI 28 mi (44 km)

Sources

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

Station coordinates: 42.6508, -88.2544.