U.S. Frost Dates by Weather Station

NOAA station USC00473756 · Wisconsin

Frost Dates for Horicon, WI

NOAA weather station Horicon WWTP (USC00473756), Wisconsin · elevation 881 ft (269 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 19only 1 spring in 10 still has a frost later
  • Typical last frostMay 150% chance of a frost after it
  • Typical first fall frostOctober 1050% chance of a frost before it
  • Frost-free season158 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Horicon, WISpring: a frost after April 16 in 9 years out of 10, after May 1 in half of the years, after May 19 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 10 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 158 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 1First frost ~Oct 10Frost season at Horicon, WISpring: a frost after April 16 in 9 years out of 10, after May 1 in half of the years, after May 19 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 10 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 158 days.JFMAMJJASONDLast frost ~May 1First frost ~Oct 10
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 19September 27
50% (typical)May 1October 10
90% (likely)April 16October 24
Frost-free season (32°F, 50% chance)
158 days
Hard frost (28°F), last in spring, 50% chance after
April 20
Hard frost (28°F), first in fall, 50% chance before
October 21

The last 15 years (2006–2020 normals)

Typical last frost April 30 (1 day earlier than the 30-year normal), typical first fall frost October 12 (2 days later). Frost-free season 163 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 Horicon: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 19, 20% May 13, 30% May 8, 40% May 5, 50% May 1, 60% April 29, 70% April 26, 80% April 22, 90% April 16. Observed last spring frost in recent years: 2021 May 11, 2022 May 4, 2023 April 26, 2024 April 25, 2025 April 17, 2026 May 8.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 19May 1Apr 162021: May 112022: May 42023: April 262024: April 252025: April 172026: May 8Fall at Horicon: chance of a frost before this dateFall, chance of a frost before the date: 10% September 27, 20% September 30, 30% October 4, 40% October 7, 50% October 10, 60% October 13, 70% October 16, 80% October 19, 90% October 24. Observed first fall frost in recent years: 2021 October 22, 2022 October 8, 2023 October 17, 2024 October 8, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 10Oct 242021: October 222022: October 82023: October 172024: October 82025: 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 11October 22
2022May 4October 8
2023April 26October 17
2024April 25October 8
2025April 17October 24
2026May 8season not over yet

What these dates mean

September 27 is the cautious fall date for finishing the harvest of tender crops in Horicon, where there is only a 10% chance that a light frost has arrived earlier. Gardeners can expect the median point for autumn light frosts on October 10, a 50% date that represents an even odds of a frost occurring earlier.

In spring the cautious date for setting out tender crops is May 19, when the chance of a light frost later than that date is just 10%; the early gamble date is April 16 with a 90% chance. The median spring point is May 1, the 50% date, indicating a 50% chance of a frost later than this date. Hard frosts at 28°F are tracked separately, with the 50% dates on April 20 in spring and October 21 in fall; these colder events can damage plants more severely than the 32°F light frosts.

How to read the probabilities

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

  • Spring: "10% after May 19" 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 27" 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 Horicon, WINumbered nearest stations: 1 — Beaver Dam, WI — 11 mi; 2 — Hartford, WI — 13 mi; 3 — Watertown, WI — 19 mi; 4 — Oconomowoc, WI — 24 mi; 5 — Fond du Lac, WI — 26 mi.25 mi · 40 km1. Beaver Dam, WI — 11 mi12. Hartford, WI — 13 mi23. Watertown, WI — 19 mi34. Oconomowoc, WI — 24 mi45. Fond du Lac, WI — 26 mi5
  1. Beaver Dam, WI 11 mi (17 km)
  2. Hartford, WI 13 mi (21 km)
  3. Watertown, WI 19 mi (31 km)
  4. Oconomowoc, WI 24 mi (39 km)
  5. Fond du Lac, WI 26 mi (42 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: 43.4389, -88.6314.