U.S. Frost Dates by Weather Station

NOAA station USC00218986 · Minnesota

Frost Dates for Wild River State Park, MN

NOAA weather station Wild River State Park (USC00218986), Minnesota · elevation 840 ft (256 m) · hardiness zone 4a*

  • Lower-risk planting dateafter June 3only 1 spring in 10 still has a frost later
  • Typical last frostMay 1950% chance of a frost after it
  • Typical first fall frostSeptember 2550% chance of a frost before it
  • Frost-free season128 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Wild River State Park, MNSpring: a frost after May 2 in 9 years out of 10, after May 19 in half of the years, after June 3 in 1 year out of 10. Fall: the first frost comes before September 10 in 1 year out of 10, before September 25 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 128 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 19First frost ~Sep 25Frost season at Wild River State Park, MNSpring: a frost after May 2 in 9 years out of 10, after May 19 in half of the years, after June 3 in 1 year out of 10. Fall: the first frost comes before September 10 in 1 year out of 10, before September 25 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 128 days.JFMAMJJASONDLast frost ~May 19First frost ~Sep 25
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)June 3September 10
50% (typical)May 19September 25
90% (likely)May 2October 8
Frost-free season (32°F, 50% chance)
128 days
Hard frost (28°F), last in spring, 50% chance after
May 6
Hard frost (28°F), first in fall, 50% chance before
October 4

The last 15 years (2006–2020 normals)

Typical last frost May 16 (3 days earlier than the 30-year normal), typical first fall frost September 27 (2 days later). Frost-free season 132 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 Wild River State Park: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 3, 20% May 29, 30% May 26, 40% May 22, 50% May 19, 60% May 16, 70% May 12, 80% May 7, 90% May 2. Observed last spring frost in recent years: 2023 May 3, 2025 May 24, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 3May 19May 22023: May 32025: May 242026: May 20Fall at Wild River State Park: chance of a frost before this dateFall, chance of a frost before the date: 10% September 10, 20% September 15, 30% September 19, 40% September 22, 50% September 25, 60% September 28, 70% October 1, 80% October 4, 90% October 8. Observed first fall frost in recent years: 2021 October 16, 2022 September 27, 2023 October 9, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 10Sep 25Oct 82021: October 162022: September 272023: October 92025: 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
2021incomplete recordOctober 16
2022incomplete recordSeptember 27
2023May 3October 9
2024incomplete recordincomplete record
2025May 24October 8
2026May 20season not over yet

What these dates mean

September 10 is the cautious fall date for finishing the harvest of tender crops in Wild River State Park; only a 10 % chance exists that a light frost has arrived earlier.

For light frosts (32 °F) the 50 % dates are May 19 in spring and September 25 in fall. At the May 19 marker there is an even chance that a light frost will occur later, while at September 25 there is an even chance that a light frost has already occurred earlier. Gardeners who prefer to limit risk would plan to set out tender crops after the cautious spring date of June 3 (10 % chance of a frost later) and to conclude harvest before the cautious fall date of September 10.

Hard frosts (28 °F) are more damaging than light frosts, which is why the median hard-frost dates are noted as May 6 and October 4.

How to read the probabilities

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

  • Spring: "10% after June 3" 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 10" 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 Wild River State Park, MNNumbered nearest stations: 1 — St. Croix Falls, WI — 9 mi; 2 — Luck, WI — 13 mi; 3 — Forest Lake, MN — 15 mi; 4 — Grantsburg, WI — 17 mi; 5 — Amery, WI — 24 mi.WIMN25 mi · 40 km1. St. Croix Falls, WI — 9 mi12. Luck, WI — 13 mi23. Forest Lake, MN — 15 mi34. Grantsburg, WI — 17 mi45. Amery, WI — 24 mi5
  1. St. Croix Falls, WI 9 mi (15 km)
  2. Luck, WI 13 mi (21 km)
  3. Forest Lake, MN 15 mi (24 km)
  4. Grantsburg, WI 17 mi (28 km)
  5. Amery, WI 24 mi (39 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: 45.5231, -92.7489.