U.S. Frost Dates by Weather Station

NOAA station USC00216654 · Minnesota

Frost Dates for Preston, MN

NOAA weather station Preston (USC00216654), Minnesota · elevation 930 ft (284 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 27only 1 spring in 10 still has a frost later
  • Typical last frostMay 1450% chance of a frost after it
  • Typical first fall frostSeptember 2850% chance of a frost before it
  • Frost-free season136 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Preston, MNSpring: a frost after May 1 in 9 years out of 10, after May 14 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 28 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 136 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 14First frost ~Sep 28Frost season at Preston, MNSpring: a frost after May 1 in 9 years out of 10, after May 14 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 28 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 136 days.JFMAMJJASONDLast frost ~May 14First frost ~Sep 28
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 27September 15
50% (typical)May 14September 28
90% (likely)May 1October 9
Frost-free season (32°F, 50% chance)
136 days
Hard frost (28°F), last in spring, 50% chance after
May 4
Hard frost (28°F), first in fall, 50% chance before
October 5

The last 15 years (2006–2020 normals)

Typical last frost May 12 (2 days earlier than the 30-year normal), typical first fall frost October 1 (3 days later). Frost-free season 140 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 Preston: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 27, 20% May 23, 30% May 20, 40% May 16, 50% May 14, 60% May 11, 70% May 9, 80% May 5, 90% May 1. Observed last spring frost in recent years: 2021 May 29, 2022 May 24, 2025 April 27, 2026 May 12.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 27May 14May 12021: May 292022: May 242025: April 272026: May 12Fall at Preston: chance of a frost before this dateFall, chance of a frost before the date: 10% September 15, 20% September 19, 30% September 22, 40% September 25, 50% September 28, 60% September 30, 70% October 2, 80% October 5, 90% October 9. Observed first fall frost in recent years: 2021 October 17, 2022 September 28, 2023 October 9, 2024 October 7, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 15Sep 28Oct 92021: October 172022: September 282023: October 92024: October 72025: 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
2021May 29October 17
2022May 24September 28
2023incomplete recordOctober 9
2024incomplete recordOctober 7
2025April 27October 8
2026May 12season not over yet

What these dates mean

Setting out tender crops on the early spring date of May 1 in Preston carries a 90 % chance that a light frost will still occur later, making it a gamble. The cautious alternative is May 27, when only a 10 % chance of a later frost remains, providing a lower-risk window for planting.

The 50 % dates are May 14 for spring and September 28 for fall; on each of these days the odds of a light frost are even, meaning a gardener has an equal chance of experiencing frost later (spring) or earlier (fall). For a careful schedule the fall cautious date is September 15, when there is just a 10 % chance a frost has already arrived. The hard-frost median dates are May 4 and October 5, and a hard frost at 28 °F can injure plants more severely than a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after May 27" 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 15" 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 Preston, MNNumbered nearest stations: 1 — Rushford, MN — 19 mi; 2 — Cresco, IA — 20 mi; 3 — Grand Meadow, MN — 25 mi; 4 — Rochester, MN — 26 mi; 5 — Caledonia, MN — 29 mi.MNIAWI25 mi · 40 km1. Rushford, MN — 19 mi12. Cresco, IA — 20 mi23. Grand Meadow, MN — 25 mi34. Rochester, MN — 26 mi45. Caledonia, MN — 29 mi5
  1. Rushford, MN 19 mi (30 km)
  2. Cresco, IA 20 mi (32 km)
  3. Grand Meadow, MN 25 mi (40 km)
  4. Rochester, MN 26 mi (42 km)
  5. Caledonia, MN 29 mi (46 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: 43.6725, -92.0747.