U.S. Frost Dates by Weather Station

NOAA station USC00216787 · Minnesota

Frost Dates for Red Lake Falls, MN

NOAA weather station Red Lake Falls (USC00216787), Minnesota · elevation 1038 ft (316 m) · hardiness zone 3b*

  • Lower-risk planting dateafter May 24only 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 season142 daystypical year, 32°F
  • Hardiness zone3bcalculated*

The year at a glance

Frost season at Red Lake Falls, MNSpring: a frost after April 27 in 9 years out of 10, after May 9 in half of the years, after May 24 in 1 year out of 10. Fall: the first frost comes before September 16 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: 142 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 9First frost ~Sep 30Frost season at Red Lake Falls, MNSpring: a frost after April 27 in 9 years out of 10, after May 9 in half of the years, after May 24 in 1 year out of 10. Fall: the first frost comes before September 16 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: 142 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.

Frost dates (32°F)

Probability of frost, based on 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 24September 16
50% (typical)May 9September 30
90% (likely)April 27October 11
Frost-free season (32°F, 50% chance)
142 days
Hard frost (28°F), last in spring, 50% chance after
April 30
Hard frost (28°F), first in fall, 50% chance before
October 8

The last 15 years (2006–2020 normals)

Typical last frost May 9 (same as the 30-year normal), typical first fall frost October 2 (2 days later). Frost-free season 146 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 Red Lake Falls: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 24, 20% May 19, 30% May 15, 40% May 12, 50% May 9, 60% May 6, 70% May 4, 80% May 1, 90% April 27. Observed last spring frost in recent years: 2021 May 8, 2022 May 4, 2023 May 3, 2024 April 25, 2025 April 30, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 24May 9Apr 272021: May 82022: May 42023: May 32024: April 252025: April 302026: May 20Fall at Red Lake Falls: chance of a frost before this dateFall, chance of a frost before the date: 10% September 16, 20% September 20, 30% September 24, 40% September 27, 50% September 30, 60% October 1, 70% October 4, 80% October 7, 90% October 11. Observed first fall frost in recent years: 2021 October 21, 2022 September 28, 2023 October 10, 2024 October 14, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 16Sep 30Oct 112021: October 212022: September 282023: October 102024: 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 8October 21
2022May 4September 28
2023May 3October 10
2024April 25October 14
2025April 30October 8
2026May 20season not over yet

What these dates mean

Setting out tender crops on the early spring date, April 27, is a gamble that carries a 90 % chance of a frost later in Red Lake Falls. The cautious alternative is the later May 24 date, which leaves only a 10 % chance of a frost after planting.

For a light frost, the 50 % date is May 9, marking the point where the chance of a frost reaches 50 %, while the hard-frost median date is April 30. In the fall, the 50 % date for light frost is September 30, marking the point where the chance of a frost reaches 50 %, and the hard-frost median date is October 8. A cautious plan therefore uses May 24 for setting out tender crops in spring and September 16 for finishing harvest in fall, each with only a 10 % chance of a frost occurring before or after, respectively.

A hard frost at 28 °F can injure plants that would survive a light frost at 32 °F, making it a more severe threat to tender crops.

How to read the probabilities

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

  • Spring: "10% after May 24" 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 16" 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 Red Lake Falls, MNNumbered nearest stations: 1 — near Crookston, MN — 16 mi; 2 — near Grand Forks, ND — 38 mi; 3 — Argyle, MN — 40 mi; 4 — Grand Forks (Airport), ND — 42 mi; 5 — Thorhult, MN — 53 mi.MN25 mi · 40 km1. near Crookston, MN — 16 mi12. near Grand Forks, ND — 38 mi23. Argyle, MN — 40 mi34. Grand Forks (Airport), ND — 42 mi45. Thorhult, MN — 53 mi5
  1. near Crookston, MN 16 mi (26 km)
  2. near Grand Forks, ND 38 mi (61 km)
  3. Argyle, MN 40 mi (64 km)
  4. Grand Forks (Airport), ND 42 mi (67 km)
  5. Thorhult, MN 53 mi (85 km)

Sources

* Hardiness zone 3b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 47.8794, -96.2844.