U.S. Frost Dates by Weather Station

NOAA station USC00473038 · Wisconsin

Frost Dates for Genoa Dam 8, WI

NOAA weather station Genoa Dam 8 (USC00473038), Wisconsin · elevation 639 ft (195 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 5only 1 spring in 10 still has a frost later
  • Typical last frostApril 2250% chance of a frost after it
  • Typical first fall frostOctober 1750% chance of a frost before it
  • Frost-free season178 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Genoa Dam 8, WISpring: a frost after April 6 in 9 years out of 10, after April 22 in half of the years, after May 5 in 1 year out of 10. Fall: the first frost comes before October 4 in 1 year out of 10, before October 17 in half of the years, before October 31 in 9 years out of 10. Typical frost-free season: 178 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 22First frost ~Oct 17Frost season at Genoa Dam 8, WISpring: a frost after April 6 in 9 years out of 10, after April 22 in half of the years, after May 5 in 1 year out of 10. Fall: the first frost comes before October 4 in 1 year out of 10, before October 17 in half of the years, before October 31 in 9 years out of 10. Typical frost-free season: 178 days.JFMAMJJASONDLast frost ~Apr 22First frost ~Oct 17
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 5October 4
50% (typical)April 22October 17
90% (likely)April 6October 31
Frost-free season (32°F, 50% chance)
178 days
Hard frost (28°F), last in spring, 50% chance after
April 10
Hard frost (28°F), first in fall, 50% chance before
October 28

The last 15 years (2006–2020 normals)

Typical last frost April 19 (3 days earlier than the 30-year normal), typical first fall frost October 20 (3 days later). Frost-free season 183 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 Genoa Dam 8: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 5, 20% May 1, 30% April 28, 40% April 24, 50% April 22, 60% April 19, 70% April 15, 80% April 11, 90% April 6. Observed last spring frost in recent years: 2021 April 26, 2022 April 27, 2023 April 27, 2024 April 22, 2025 April 17, 2026 April 21.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 5Apr 22Apr 62021: April 262022: April 272023: April 272024: April 222025: April 172026: April 21Fall at Genoa Dam 8: chance of a frost before this dateFall, chance of a frost before the date: 10% October 4, 20% October 8, 30% October 12, 40% October 14, 50% October 17, 60% October 20, 70% October 23, 80% October 26, 90% October 31. Observed first fall frost in recent years: 2021 October 25, 2022 October 16, 2023 October 12, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 4Oct 17Oct 312021: October 252022: October 162023: October 122024: 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
2021April 26October 25
2022April 27October 16
2023April 27October 12
2024April 22October 16
2025April 17October 24
2026April 21season not over yet

What these dates mean

The 178 days between the 50% dates in Genoa Dam 8 frame the growing window: the 50% date of April 22 marks the point at which a frost is equally likely to occur later, and the 50% date of October 17 marks the point at which a frost is equally likely to have occurred earlier. Within that span, most tender crops can be grown if they avoid the higher-risk dates.

A cautious planting plan for tender crops follows the 10 % spring date of May 5, when only a small chance of a later frost remains, and the 10 % fall date of October 4, when only a small chance that a frost has already arrived. Planting on April 6 or harvesting on October 31 carries a 90 % chance of frost and is a gamble. The hard-frost 50 % dates of April 10 and October 28 highlight that a 28°F frost can injure plants that survive a 32°F light frost, so the colder threshold is more consequential.

How to read the probabilities

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

  • Spring: "10% after May 5" 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 October 4" 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 Genoa Dam 8, WINumbered nearest stations: 1 — Caledonia, MN — 14 mi; 2 — Viroqua, WI — 18 mi; 3 — La Crosse, WI — 21 mi; 4 — Lynxville Dam 9, WI — 26 mi; 5 — Gays Mills, WI — 26 mi.WIIAMN25 mi · 40 km1. Caledonia, MN — 14 mi12. Viroqua, WI — 18 mi23. La Crosse, WI — 21 mi34. Lynxville Dam 9, WI — 26 mi45. Gays Mills, WI — 26 mi5
  1. Caledonia, MN 14 mi (23 km)
  2. Viroqua, WI 18 mi (28 km)
  3. La Crosse, WI 21 mi (34 km)
  4. Lynxville Dam 9, WI 26 mi (41 km)
  5. Gays Mills, 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: 43.5706, -91.2294.