U.S. Frost Dates by Weather Station

NOAA station USC00219046 · Minnesota

Frost Dates for Winnebago, MN

NOAA weather station Winnebago (USC00219046), Minnesota · elevation 1110 ft (338 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 8only 1 spring in 10 still has a frost later
  • Typical last frostApril 2750% chance of a frost after it
  • Typical first fall frostOctober 1050% chance of a frost before it
  • Frost-free season166 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Winnebago, MNSpring: a frost after April 10 in 9 years out of 10, after April 27 in half of the years, after May 8 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 23 in 9 years out of 10. Typical frost-free season: 166 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 27First frost ~Oct 10Frost season at Winnebago, MNSpring: a frost after April 10 in 9 years out of 10, after April 27 in half of the years, after May 8 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 23 in 9 years out of 10. Typical frost-free season: 166 days.JFMAMJJASONDLast frost ~Apr 27First 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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 8September 27
50% (typical)April 27October 10
90% (likely)April 10October 23
Frost-free season (32°F, 50% chance)
166 days
Hard frost (28°F), last in spring, 50% chance after
April 15
Hard frost (28°F), first in fall, 50% chance before
October 20

The last 15 years (2006–2020 normals)

Typical last frost April 28 (1 day later than the 30-year normal), typical first fall frost October 13 (3 days later). Frost-free season 168 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 Winnebago: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 8, 20% May 5, 30% May 2, 40% April 30, 50% April 27, 60% April 24, 70% April 20, 80% April 16, 90% April 10. Observed last spring frost in recent years: 2021 April 25, 2022 April 27, 2023 April 26, 2024 April 21, 2025 April 20, 2026 April 21.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 8Apr 27Apr 102021: April 252022: April 272023: April 262024: April 212025: April 202026: April 21Fall at Winnebago: chance of a frost before this dateFall, chance of a frost before the date: 10% September 27, 20% October 1, 30% October 4, 40% October 7, 50% October 10, 60% October 13, 70% October 16, 80% October 19, 90% October 23. Observed first fall frost in recent years: 2021 October 23, 2022 October 8, 2023 October 28, 2024 October 15.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 10Oct 232021: October 232022: October 82023: October 282024: October 15
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 23
2022April 27October 8
2023April 26October 28
2024April 21October 15
2025April 20incomplete record
2026April 21season not over yet

What these dates mean

Setting out tender crops on April 10 in Winnebago carries a 90% chance of a light frost later, making it a gamble.

A cautious spring schedule uses the May 8 date, when only a 10% chance of a light frost remains, while a cautious fall schedule finishes tender crops by September 27, a date with only a 10% chance that a frost has already arrived. The 50% spring date is April 27; there is an even chance of a light frost later than this date. The 50% fall date is October 10, marking a 50% chance of a light frost earlier than this date. Hard-frost median dates are April 15 and October 20.

Hard frost at 28 °F can injure plants that survive a 32 °F light frost, so it represents a more serious risk.

How to read the probabilities

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

  • Spring: "10% after May 8" 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 Winnebago, MNNumbered nearest stations: 1 — Amboy, MN — 8 mi; 2 — Saint James, MN — 27 mi; 3 — near Waseca, MN — 38 mi; 4 — Estherville, IA — 38 mi; 5 — St. Peter, MN — 40 mi.IA25 mi · 40 km1. Amboy, MN — 8 mi12. Saint James, MN — 27 mi23. near Waseca, MN — 38 mi34. Estherville, IA — 38 mi45. St. Peter, MN — 40 mi5
  1. Amboy, MN 8 mi (13 km)
  2. Saint James, MN 27 mi (44 km)
  3. near Waseca, MN 38 mi (62 km)
  4. Estherville, IA 38 mi (62 km)
  5. St. Peter, MN 40 mi (64 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: 43.7639, -94.1661.