U.S. Frost Dates by Weather Station

NOAA station USC00479319 · Wisconsin

Frost Dates for Wisconsin Dells, WI

NOAA weather station Wisconsin Dells (USC00479319), Wisconsin · elevation 835 ft (255 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 22only 1 spring in 10 still has a frost later
  • Typical last frostMay 850% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season146 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Wisconsin Dells, WISpring: a frost after April 24 in 9 years out of 10, after May 8 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 3 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 146 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 8First frost ~Oct 3Frost season at Wisconsin Dells, WISpring: a frost after April 24 in 9 years out of 10, after May 8 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 3 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 146 days.JFMAMJJASONDLast frost ~May 8First frost ~Oct 3
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 22September 21
50% (typical)May 8October 3
90% (likely)April 24October 16
Frost-free season (32°F, 50% chance)
146 days
Hard frost (28°F), last in spring, 50% chance after
April 28
Hard frost (28°F), first in fall, 50% chance before
October 14

The last 15 years (2006–2020 normals)

Typical last frost May 7 (1 day earlier than the 30-year normal), typical first fall frost October 7 (4 days later). Frost-free season 152 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 Wisconsin Dells: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 22, 20% May 17, 30% May 14, 40% May 11, 50% May 8, 60% May 4, 70% May 2, 80% April 29, 90% April 24. Observed last spring frost in recent years: 2021 May 29, 2022 May 5, 2023 April 26, 2024 April 26, 2025 May 9.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 22May 8Apr 242021: May 292022: May 52023: April 262024: April 262025: May 9Fall at Wisconsin Dells: 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 3, 60% October 5, 70% October 8, 80% October 12, 90% October 16. Observed first fall frost in recent years: 2021 October 17, 2022 September 29, 2023 October 9, 2024 October 7, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 21Oct 3Oct 162021: October 172022: September 292023: October 92024: October 72025: 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 17
2022May 5September 29
2023April 26October 9
2024April 26October 7
2025May 9October 8
2026incomplete recordseason not over yet

What these dates mean

May 22 is the cautious spring date for tender crops in Wisconsin Dells, allowing a gardener to set them out with only a 10 % chance of a later light frost. The earlier date, April 24, carries a 90 % chance of a frost and therefore is a gamble for tender plants. The 50% date, May 8, marks the point where there is an even chance of a light frost occurring later in the season.

In fall, September 21 is the cautious date to finish harvesting tender crops, with only a 10 % chance that a light frost has already arrived; the later date, October 16, has a 90 % chance of frost and is a gamble. The 50% date, October 3, indicates an even chance of a light frost earlier. Hard frost at 28 °F, whose median dates are April 28 and October 14, can damage plants more severely 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 22" 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 Wisconsin Dells, WINumbered nearest stations: 1 — Portage, WI — 17 mi; 2 — Mauston, WI — 19 mi; 3 — Montello, WI — 25 mi; 4 — Arlington, WI — 30 mi; 5 — Hancock Experiment Farm, WI — 37 mi.IA25 mi · 40 km1. Portage, WI — 17 mi12. Mauston, WI — 19 mi23. Montello, WI — 25 mi34. Arlington, WI — 30 mi45. Hancock Experiment Farm, WI — 37 mi5
  1. Portage, WI 17 mi (28 km)
  2. Mauston, WI 19 mi (31 km)
  3. Montello, WI 25 mi (41 km)
  4. Arlington, WI 30 mi (48 km)
  5. Hancock Experiment Farm, WI 37 mi (60 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: 43.6089, -89.7667.