U.S. Frost Dates by Weather Station

NOAA station USC00218907 · Minnesota

Frost Dates for Wheaton, MN

NOAA weather station Wheaton (USC00218907), Minnesota · elevation 1018 ft (310 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 12only 1 spring in 10 still has a frost later
  • Typical last frostMay 150% chance of a frost after it
  • Typical first fall frostOctober 950% chance of a frost before it
  • Frost-free season160 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Wheaton, MNSpring: a frost after April 18 in 9 years out of 10, after May 1 in half of the years, after May 12 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 9 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 160 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 1First frost ~Oct 9Frost season at Wheaton, MNSpring: a frost after April 18 in 9 years out of 10, after May 1 in half of the years, after May 12 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 9 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 160 days.JFMAMJJASONDLast frost ~May 1First frost ~Oct 9
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 12September 26
50% (typical)May 1October 9
90% (likely)April 18October 23
Frost-free season (32°F, 50% chance)
160 days
Hard frost (28°F), last in spring, 50% chance after
April 21
Hard frost (28°F), first in fall, 50% chance before
October 20

The last 15 years (2006–2020 normals)

Typical last frost April 30 (1 day earlier than the 30-year normal), typical first fall frost October 13 (4 days later). Frost-free season 166 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 Wheaton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 12, 20% May 8, 30% May 5, 40% May 2, 50% May 1, 60% April 29, 70% April 26, 80% April 23, 90% April 18. Observed last spring frost in recent years: 2021 May 11, 2022 April 28, 2023 April 26, 2024 April 24, 2025 April 30, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1May 12May 1Apr 182021: May 112022: April 282023: April 262024: April 242025: April 302026: May 11Fall at Wheaton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 26, 20% September 30, 30% October 4, 40% October 6, 50% October 9, 60% October 12, 70% October 15, 80% October 19, 90% October 23. Observed first fall frost in recent years: 2021 October 21, 2022 October 7, 2023 October 7, 2024 October 15, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 26Oct 9Oct 232021: October 212022: October 72023: October 72024: October 152025: October 22
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 11October 21
2022April 28October 7
2023April 26October 7
2024April 24October 15
2025April 30October 22
2026May 11season not over yet

What these dates mean

May 12 is the cautious spring light-frost date for Wheaton; with only a 10 % chance of a frost later, it marks the point when a gardener can set out tender crops with minimal risk. The median light-frost date, May 1, carries a 50 % chance of a frost later, while the median hard-frost date, April 21, carries a 50 % chance of a hard frost later; these dates simply indicate where the odds split. In fall, September 26 serves as the cautious light-frost date, offering a 10 % chance of a frost earlier and therefore the appropriate time to finish harvesting tender crops. The median light-frost date, October 9, has a 50 % chance of a frost earlier, and the median hard-frost date, October 20, reflects a 50 % chance of a hard frost earlier. A hard frost at 28 °F can cause far more damage to plant tissue 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 12" 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 26" 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 Wheaton, MNNumbered nearest stations: 1 — Victor, SD — 18 mi; 2 — Browns Valley, MN — 21 mi; 3 — Sisseton, SD — 28 mi; 4 — near Morris, MN — 34 mi; 5 — Artichoke Lake 1 E, MN — 34 mi.SDND25 mi · 40 km1. Victor, SD — 18 mi12. Browns Valley, MN — 21 mi23. Sisseton, SD — 28 mi34. near Morris, MN — 34 mi45. Artichoke Lake 1 E, MN — 34 mi5
  1. Victor, SD 18 mi (28 km)
  2. Browns Valley, MN 21 mi (35 km)
  3. Sisseton, SD 28 mi (44 km)
  4. near Morris, MN 34 mi (55 km)
  5. Artichoke Lake 1 E, MN 34 mi (55 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: 45.8081, -96.5042.