U.S. Frost Dates by Weather Station

NOAA station USC00215400 · Minnesota

Frost Dates for Milan, MN

NOAA weather station Milan 1 NW (USC00215400), Minnesota · elevation 1020 ft (311 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 350% chance of a frost after it
  • Typical first fall frostOctober 250% chance of a frost before it
  • Frost-free season151 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Milan, MNSpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before October 2 in half of the years, before October 15 in 9 years out of 10. Typical frost-free season: 151 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 3First frost ~Oct 2Frost season at Milan, MNSpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before October 2 in half of the years, before October 15 in 9 years out of 10. Typical frost-free season: 151 days.JFMAMJJASONDLast frost ~May 3First frost ~Oct 2
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 17September 18
50% (typical)May 3October 2
90% (likely)April 20October 15
Frost-free season (32°F, 50% chance)
151 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
October 12

The last 15 years (2006–2020 normals)

Typical last frost May 4 (1 day later than the 30-year normal), typical first fall frost October 5 (3 days later). Frost-free season 152 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 Milan: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 12, 30% May 9, 40% May 5, 50% May 3, 60% April 30, 70% April 28, 80% April 25, 90% April 20. Observed last spring frost in recent years: 2021 May 11, 2022 April 28, 2023 May 3, 2024 April 24, 2025 May 3, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 3Apr 202021: May 112022: April 282023: May 32024: April 242025: May 32026: May 20Fall at Milan: chance of a frost before this dateFall, chance of a frost before the date: 10% September 18, 20% September 23, 30% September 27, 40% September 30, 50% October 2, 60% October 4, 70% October 7, 80% October 10, 90% October 15. Observed first fall frost in recent years: 2021 October 21, 2022 September 28, 2023 October 7, 2024 October 4, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 18Oct 2Oct 152021: October 212022: September 282023: October 72024: October 42025: October 7
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 21
2022April 28September 28
2023May 3October 7
2024April 24October 4
2025May 3October 7
2026May 20season not over yet

What these dates mean

The 151 days between the 50% dates in Milan—May 3 and October 2—define the period in which light frosts are equally likely to occur or not, giving gardeners a clear span for most growing activities. The 50% dates themselves are not frost dates; they simply mark the median point of the historical probability curve for a 32 °F frost.

For a cautious plan, tender crops should be set out after the spring cautious date of May 17, when only a 10 % chance of a later light frost remains, and should be finished by the fall cautious date of September 18, when there is just a 10 % chance that a light frost has already arrived. A hard frost at 28 °F is more critical than a light frost because it can damage plant tissue that survives a 32 °F frost, and the median hard-frost dates are April 23 in spring and October 12 in fall.

How to read the probabilities

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

  • Spring: "10% after May 17" 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 18" 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 Milan, MNNumbered nearest stations: 1 — Madison, MN — 14 mi; 2 — Benson, MN — 20 mi; 3 — Artichoke Lake 1 E, MN — 21 mi; 4 — near Morris, MN — 32 mi; 5 — Canby, MN — 33 mi.MNSD25 mi · 40 km1. Madison, MN — 14 mi12. Benson, MN — 20 mi23. Artichoke Lake 1 E, MN — 21 mi34. near Morris, MN — 32 mi45. Canby, MN — 33 mi5
  1. Madison, MN 14 mi (23 km)
  2. Benson, MN 20 mi (33 km)
  3. Artichoke Lake 1 E, MN 21 mi (33 km)
  4. near Morris, MN 32 mi (52 km)
  5. Canby, MN 33 mi (52 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: 45.1219, -95.9269.