U.S. Frost Dates by Weather Station

NOAA station USC00478589 · Wisconsin

Frost Dates near Trempealeau, WI

NOAA weather station Trempealeau Dam 6 (USC00478589), Wisconsin · elevation 660 ft (201 m) · hardiness zone 5a*

Trempealeau is the nearest town to the station (0.5 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter May 13only 1 spring in 10 still has a frost later
  • Typical last frostApril 2950% chance of a frost after it
  • Typical first fall frostOctober 1150% chance of a frost before it
  • Frost-free season165 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season near Trempealeau, WISpring: a frost after April 11 in 9 years out of 10, after April 29 in half of the years, after May 13 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 11 in half of the years, before October 26 in 9 years out of 10. Typical frost-free season: 165 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 29First frost ~Oct 11Frost season near Trempealeau, WISpring: a frost after April 11 in 9 years out of 10, after April 29 in half of the years, after May 13 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 11 in half of the years, before October 26 in 9 years out of 10. Typical frost-free season: 165 days.JFMAMJJASONDLast frost ~Apr 29First frost ~Oct 11
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 13September 26
50% (typical)April 29October 11
90% (likely)April 11October 26
Frost-free season (32°F, 50% chance)
165 days
Hard frost (28°F), last in spring, 50% chance after
April 17
Hard frost (28°F), first in fall, 50% chance before
October 23

The last 15 years (2006–2020 normals)

Typical last frost April 27 (2 days earlier than the 30-year normal), typical first fall frost October 16 (5 days later). Frost-free season 172 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 near Trempealeau: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 13, 20% May 8, 30% May 4, 40% May 1, 50% April 29, 60% April 26, 70% April 23, 80% April 18, 90% April 11. Observed last spring frost in recent years: 2021 April 25, 2022 April 28, 2023 April 26, 2024 April 24, 2025 April 17, 2026 May 2.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 13Apr 29Apr 112021: April 252022: April 282023: April 262024: April 242025: April 172026: May 2Fall near Trempealeau: chance of a frost before this dateFall, chance of a frost before the date: 10% September 26, 20% October 2, 30% October 5, 40% October 8, 50% October 11, 60% October 14, 70% October 17, 80% October 21, 90% October 26. Observed first fall frost in recent years: 2021 October 26, 2022 October 18, 2023 October 29, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 26Oct 11Oct 262021: October 262022: October 182023: October 292024: 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 25October 26
2022April 28October 18
2023April 26October 29
2024April 24October 16
2025April 17October 24
2026May 2season not over yet

What these dates mean

The cautious fall date for finishing the harvest in the Trempealeau area is September 26, when there is only a 10 % chance that a light frost has arrived. The median 50 % date is October 11, indicating even odds for a light frost earlier in the season. The gamble date is October 26, with a 90 % chance, and the hard-frost 50 % date is October 23.

In spring, the cautious date for setting out tender crops is May 13, which carries a 10 % chance of a later light frost; the gamble date is April 11, with a 90 % chance. The median 50 % date is April 29, indicating even odds for a light frost later in the season. The hard-frost 50 % dates are April 17 and October 23; a hard frost can damage plants more severely than a light frost because it reaches a lower temperature.

How to read the probabilities

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

  • Spring: "10% after May 13" 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 26" 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 Trempealeau, WINumbered nearest stations: 1 — La Crosse, WI — 12 mi; 2 — near Winona, MN — 13 mi; 3 — Rushford, MN — 21 mi; 4 — Caledonia, MN — 26 mi; 5 — Sparta, WI — 31 mi.MN25 mi · 40 km1. La Crosse, WI — 12 mi12. near Winona, MN — 13 mi23. Rushford, MN — 21 mi34. Caledonia, MN — 26 mi45. Sparta, WI — 31 mi5
  1. La Crosse, WI 12 mi (20 km)
  2. near Winona, MN 13 mi (21 km)
  3. Rushford, MN 21 mi (33 km)
  4. Caledonia, MN 26 mi (41 km)
  5. Sparta, WI 31 mi (50 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: 43.9994, -91.4378.