U.S. Frost Dates by Weather Station

NOAA station USC00214861 · Minnesota

Frost Dates for Long Prairie, MN

NOAA weather station Long Prairie (USC00214861), Minnesota · elevation 1340 ft (408 m) · hardiness zone 4a*

  • Lower-risk planting dateafter May 28only 1 spring in 10 still has a frost later
  • Typical last frostMay 1350% chance of a frost after it
  • Typical first fall frostSeptember 2750% chance of a frost before it
  • Frost-free season134 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Long Prairie, MNSpring: a frost after May 1 in 9 years out of 10, after May 13 in half of the years, after May 28 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before September 27 in half of the years, before October 10 in 9 years out of 10. Typical frost-free season: 134 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 13First frost ~Sep 27Frost season at Long Prairie, MNSpring: a frost after May 1 in 9 years out of 10, after May 13 in half of the years, after May 28 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before September 27 in half of the years, before October 10 in 9 years out of 10. Typical frost-free season: 134 days.JFMAMJJASONDLast frost ~May 13First frost ~Sep 27
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 28September 13
50% (typical)May 13September 27
90% (likely)May 1October 10
Frost-free season (32°F, 50% chance)
134 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 10 (3 days earlier than the 30-year normal), typical first fall frost October 3 (6 days later). Frost-free season 143 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 Long Prairie: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 28, 20% May 23, 30% May 19, 40% May 16, 50% May 13, 60% May 10, 70% May 8, 80% May 5, 90% May 1. Observed last spring frost in recent years: 2021 May 30, 2022 May 22, 2023 May 4, 2024 April 25, 2025 May 4, 2026 May 21.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 28May 13May 12021: May 302022: May 222023: May 42024: April 252025: May 42026: May 21Fall at Long Prairie: chance of a frost before this dateFall, chance of a frost before the date: 10% September 13, 20% September 18, 30% September 21, 40% September 24, 50% September 27, 60% September 30, 70% October 2, 80% October 5, 90% October 10. Observed first fall frost in recent years: 2021 October 21, 2022 September 28, 2023 October 9, 2024 October 14, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 13Sep 27Oct 102021: October 212022: September 282023: October 92024: October 142025: 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 30October 21
2022May 22September 28
2023May 4October 9
2024April 25October 14
2025May 4October 8
2026May 21season not over yet

What these dates mean

September 13 is the cautious fall date in Long Prairie for finishing the harvest of tender crops; there is only a 10 % chance of a light frost arriving earlier than that day. Counting on crops to stay frost-free until October 10 is a gamble, because a light frost is expected earlier than that date 90 % of the time.

In spring the cautious date for setting out tender crops is May 28, when a light frost later than this day occurs only 10 % of the time, while planting on May 1 is a gamble with a 90 % chance of a later frost. The 50 % dates are May 13 in spring and September 27 in fall; each marks the point where the odds of a light frost are even. The 50 % hard-frost dates are May 4 and October 5. Hard frost at 28 °F can damage plants that would otherwise survive a 32 °F light frost, making it a more critical threshold.

How to read the probabilities

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

  • Spring: "10% after May 28" 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 13" 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 Long Prairie, MNNumbered nearest stations: 1 — Alexandria, MN — 25 mi; 2 — Glenwood, MN — 34 mi; 3 — near Collegeville, MN — 36 mi; 4 — near East Gull Lake, MN — 40 mi; 5 — Brainerd, MN — 42 mi.25 mi · 40 km1. Alexandria, MN — 25 mi12. Glenwood, MN — 34 mi23. near Collegeville, MN — 36 mi34. near East Gull Lake, MN — 40 mi45. Brainerd, MN — 42 mi5
  1. Alexandria, MN 25 mi (41 km)
  2. Glenwood, MN 34 mi (55 km)
  3. near Collegeville, MN 36 mi (58 km)
  4. near East Gull Lake, MN 40 mi (64 km)
  5. Brainerd, MN 42 mi (67 km)

Sources

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

Station coordinates: 45.9647, -94.8892.