U.S. Frost Dates by Weather Station

NOAA station USC00218692 · Minnesota

Frost Dates near Waseca, MN

NOAA weather station Waseca S Research & Outreach Center (USC00218692), Minnesota · elevation 1153 ft (351 m) · hardiness zone 4b*

Waseca is the nearest town to the station (1.1 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 14only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season155 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season near Waseca, MNSpring: a frost after April 17 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 4 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 155 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 4Frost season near Waseca, MNSpring: a frost after April 17 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 4 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 155 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 4
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 14September 20
50% (typical)May 2October 4
90% (likely)April 17October 17
Frost-free season (32°F, 50% chance)
155 days
Hard frost (28°F), last in spring, 50% chance after
April 20
Hard frost (28°F), first in fall, 50% chance before
October 14

The last 15 years (2006–2020 normals)

Typical last frost May 1 (1 day earlier than the 30-year normal), typical first fall frost October 7 (3 days later). Frost-free season 158 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 Waseca: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 14, 20% May 9, 30% May 6, 40% May 4, 50% May 2, 60% April 30, 70% April 26, 80% April 22, 90% April 17. Observed last spring frost in recent years: 2021 May 11, 2022 April 28, 2023 May 3, 2024 April 22, 2025 April 16, 2026 May 6.Spring: last frostChance of a frost after this date10%50%90%May 1May 14May 2Apr 172021: May 112022: April 282023: May 32024: April 222025: April 162026: May 6Fall near Waseca: chance of a frost before this dateFall, chance of a frost before the date: 10% September 20, 20% September 25, 30% September 28, 40% October 1, 50% October 4, 60% October 7, 70% October 10, 80% October 13, 90% October 17. Observed first fall frost in recent years: 2021 October 16, 2022 September 28, 2023 October 10, 2024 October 7, 2025 October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 20Oct 4Oct 172021: October 162022: September 282023: October 102024: October 72025: October 23
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 16
2022April 28September 28
2023May 3October 10
2024April 22October 7
2025April 16October 23
2026May 6season not over yet

What these dates mean

The cautious fall date for finishing the harvest in the Waseca area is September 20, when there is only a 10 % chance that a light frost has arrived.

For a gardener, the 50 % light-frost dates—May 2 in spring and October 4 in fall—mark the point at which the likelihood of a frost is even; a 50 % chance of a frost later than May 2 and earlier than October 4. The median hard-frost dates are April 20 and October 14. The interval between the two 32 °F 50 % dates spans 155 days.

A cautious plan should use the May 14 light-frost date (10 % chance of a later frost) for setting out tender crops in spring, and the September 20 date for finishing them in fall. Hard frosts at 28 °F are more damaging than light frosts at 32 °F because they can kill tissue that survives a milder chill.

How to read the probabilities

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

  • Spring: "10% after May 14" 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 20" 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 Waseca, MNNumbered nearest stations: 1 — Owatonna, MN — 15 mi; 2 — St. Peter, MN — 28 mi; 3 — Albert Lea, MN — 34 mi; 4 — Amboy, MN — 34 mi; 5 — Winnebago, MN — 38 mi.MNIAWI25 mi · 40 km1. Owatonna, MN — 15 mi12. St. Peter, MN — 28 mi23. Albert Lea, MN — 34 mi34. Amboy, MN — 34 mi45. Winnebago, MN — 38 mi5
  1. Owatonna, MN 15 mi (24 km)
  2. St. Peter, MN 28 mi (45 km)
  3. Albert Lea, MN 34 mi (55 km)
  4. Amboy, MN 34 mi (55 km)
  5. Winnebago, MN 38 mi (62 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: 44.0708, -93.5264.