U.S. Frost Dates by Weather Station

NOAA station USC00219249 · Minnesota

Frost Dates for Zumbrota, MN

NOAA weather station Zumbrota (USC00219249), Minnesota · elevation 970 ft (296 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 22only 1 spring in 10 still has a frost later
  • Typical last frostMay 950% chance of a frost after it
  • Typical first fall frostSeptember 3050% chance of a frost before it
  • Frost-free season144 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Zumbrota, MNSpring: a frost after April 24 in 9 years out of 10, after May 9 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before September 30 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 144 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 9First frost ~Sep 30Frost season at Zumbrota, MNSpring: a frost after April 24 in 9 years out of 10, after May 9 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before September 30 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 144 days.JFMAMJJASONDLast frost ~May 9First frost ~Sep 30
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.Today

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 22September 17
50% (typical)May 9September 30
90% (likely)April 24October 11
Frost-free season (32°F, 50% chance)
144 days
Hard frost (28°F), last in spring, 50% chance after
April 28
Hard frost (28°F), first in fall, 50% chance before
October 8

The last 15 years (2006–2020 normals)

Typical last frost May 7 (2 days earlier than the 30-year normal), typical first fall frost October 4 (4 days later). Frost-free season 151 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 Zumbrota: 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 9, 60% May 6, 70% May 3, 80% April 29, 90% April 24. Observed last spring frost in recent years: 2022 May 23, 2023 May 4, 2024 April 25, 2025 April 30, 2026 May 10.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 22May 9Apr 242022: May 232023: May 42024: April 252025: April 302026: May 10Fall at Zumbrota: chance of a frost before this dateFall, chance of a frost before the date: 10% September 17, 20% September 22, 30% September 25, 40% September 28, 50% September 30, 60% October 2, 70% October 4, 80% October 7, 90% October 11. Observed first fall frost in recent years: 2022 September 28, 2023 October 10, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 17Sep 30Oct 112022: September 282023: October 102025: 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
2021incomplete recordincomplete record
2022May 23September 28
2023May 4October 10
2024April 25incomplete record
2025April 30October 8
2026May 10season not over yet

What these dates mean

Planting tender crops on the early spring date of April 24 in Zumbrota carries a 90 % chance of encountering a light frost, making it a gamble for growers.

The 50% date in spring is May 9, which reflects an even chance of a light frost later than this date; the 50% date in fall is September 30, indicating an equal chance of a light frost earlier than this date. A cautious plan would wait until the May 22 date, which has only a 10 % chance of a later frost, and would finish tender crops by the September 17 date, which has a 10 % chance of an earlier frost.

The median hard-frost dates are April 28 in spring and October 8 in fall, and a hard frost at 28 °F can damage plant tissue that would survive a light frost at 32 °F, so it matters more than a light frost.

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 17" 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 Zumbrota, MNNumbered nearest stations: 1 — near Red Wing, MN — 22 mi; 2 — Theilman, MN — 23 mi; 3 — Rochester, MN — 29 mi; 4 — Owatonna, MN — 31 mi; 5 — Ellsworth, WI — 31 mi.WIIA25 mi · 40 km1. near Red Wing, MN — 22 mi12. Theilman, MN — 23 mi23. Rochester, MN — 29 mi34. Owatonna, MN — 31 mi45. Ellsworth, WI — 31 mi5
  1. near Red Wing, MN 22 mi (35 km)
  2. Theilman, MN 23 mi (38 km)
  3. Rochester, MN 29 mi (46 km)
  4. Owatonna, MN 31 mi (50 km)
  5. Ellsworth, WI 31 mi (51 km)

Sources

* Hardiness zone 4b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 44.2992, -92.6661.