U.S. Frost Dates by Weather Station

NOAA station USC00215598 · Minnesota

Frost Dates for Moose Lake, MN

NOAA weather station Moose Lake 1 SSE (USC00215598), Minnesota · elevation 1110 ft (338 m) · hardiness zone 4a*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 1250% chance of a frost after it
  • Typical first fall frostOctober 250% chance of a frost before it
  • Frost-free season144 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Moose Lake, MNSpring: a frost after April 28 in 9 years out of 10, after May 12 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 2 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 144 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 12First frost ~Oct 2Frost season at Moose Lake, MNSpring: a frost after April 28 in 9 years out of 10, after May 12 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 2 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 144 days.JFMAMJJASONDLast frost ~May 12First 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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 26September 20
50% (typical)May 12October 2
90% (likely)April 28October 17
Frost-free season (32°F, 50% chance)
144 days
Hard frost (28°F), last in spring, 50% chance after
April 30
Hard frost (28°F), first in fall, 50% chance before
October 14

The last 15 years (2006–2020 normals)

Typical last frost May 6 (6 days earlier than the 30-year normal), typical first fall frost October 10 (8 days later). Frost-free season 154 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 Moose Lake: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 21, 30% May 17, 40% May 14, 50% May 12, 60% May 9, 70% May 5, 80% May 2, 90% April 28.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 12Apr 28Fall at Moose Lake: chance of a frost before this dateFall, chance of a frost before the date: 10% September 20, 20% September 24, 30% September 28, 40% October 1, 50% October 2, 60% October 5, 70% October 8, 80% October 12, 90% October 17.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 20Oct 2Oct 17
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.

What these dates mean

September 20 is the cautious fall date in Moose Lake for finishing the harvest of tender crops, because only a 10 % chance of a light frost has arrived by then. The 50% light-frost dates—May 12 in spring and October 2 in fall—mark the points at which a gardener faces an even chance of a frost later (spring) or earlier (fall); they are not frost dates themselves. A cautious spring plan uses May 26, the date with a 10 % chance of a frost later, while the cautious fall plan relies on September 20. The 50% hard-frost dates are April 30 in spring and October 14 in fall, and a hard frost at 28 °F can damage plants that survive a light frost at 32 °F. The 32°F 50% dates are 144 days apart, based on a 28-year record.

How to read the probabilities

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

  • Spring: "10% after May 26" 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 Moose Lake, MNNumbered nearest stations: 1 — Bruno, MN — 14 mi; 2 — Wright, MN — 19 mi; 3 — Cloquet, MN — 22 mi; 4 — Floodwood, MN — 37 mi; 5 — Superior, WI — 38 mi.WI25 mi · 40 km1. Bruno, MN — 14 mi12. Wright, MN — 19 mi23. Cloquet, MN — 22 mi34. Floodwood, MN — 37 mi45. Superior, WI — 38 mi5
  1. Bruno, MN 14 mi (23 km)
  2. Wright, MN 19 mi (31 km)
  3. Cloquet, MN 22 mi (35 km)
  4. Floodwood, MN 37 mi (60 km)
  5. Superior, WI 38 mi (61 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: 46.4378, -92.7578.