U.S. Frost Dates by Weather Station

NOAA station USC00219170 · Minnesota

Frost Dates for Worthington, MN

NOAA weather station Worthington 2 NNE (USC00219170), Minnesota · elevation 1570 ft (479 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 15only 1 spring in 10 still has a frost later
  • Typical last frostMay 350% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season153 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Worthington, MNSpring: a frost after April 19 in 9 years out of 10, after May 3 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 153 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 3First frost ~Oct 4Frost season at Worthington, MNSpring: a frost after April 19 in 9 years out of 10, after May 3 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 153 days.JFMAMJJASONDLast frost ~May 3First frost ~Oct 4
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 15September 21
50% (typical)May 3October 4
90% (likely)April 19October 18
Frost-free season (32°F, 50% chance)
153 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 3 (same as the 30-year normal), typical first fall frost October 8 (4 days later). Frost-free season 157 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 Worthington: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 15, 20% May 11, 30% May 8, 40% May 5, 50% May 3, 60% May 1, 70% April 28, 80% April 24, 90% April 19. Observed last spring frost in recent years: 2021 May 12, 2022 May 4, 2023 April 26, 2024 April 24, 2025 April 20, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1May 15May 3Apr 192021: May 122022: May 42023: April 262024: April 242025: April 202026: May 11Fall at Worthington: chance of a frost before this dateFall, chance of a frost before the date: 10% September 21, 20% September 24, 30% September 28, 40% October 1, 50% October 4, 60% October 7, 70% October 10, 80% October 14, 90% October 18. Observed first fall frost in recent years: 2021 October 23, 2022 September 28, 2023 October 7, 2024 October 14, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 21Oct 4Oct 182021: October 232022: September 282023: October 72024: October 142025: 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 12October 23
2022May 4September 28
2023April 26October 7
2024April 24October 14
2025April 20October 22
2026May 11season not over yet

What these dates mean

September 21 is the cautious fall date for finishing the harvest in Worthington; only a 10 % chance exists that a light frost has arrived earlier, so ending tender-crop harvesting by that day keeps risk low.

In spring the cautious date for setting out tender crops is May 15, when there is just a 10 % chance of a later light frost; planting on April 19 carries a 90 % gamble. The 50 % dates—May 3 for light frost and October 4 for light frost—are median points with even odds and are not frost dates themselves. The hard-frost 50 % dates are April 23 and October 15, and a hard frost at 28 °F can damage plants more severely than a light frost at 32 °F. The interval between the two 32 °F 50 % dates, May 3 and October 4, spans 153 days, based on a 29-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 15" 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 21" 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 Worthington, MNNumbered nearest stations: 1 — Sibley, IA — 19 mi; 2 — Lake Park, IA — 19 mi; 3 — Milford, IA — 27 mi; 4 — Windom, MN — 28 mi; 5 — Lake Wilson, MN — 31 mi.IASD25 mi · 40 km1. Sibley, IA — 19 mi12. Lake Park, IA — 19 mi23. Milford, IA — 27 mi34. Windom, MN — 28 mi45. Lake Wilson, MN — 31 mi5
  1. Sibley, IA 19 mi (30 km)
  2. Lake Park, IA 19 mi (30 km)
  3. Milford, IA 27 mi (43 km)
  4. Windom, MN 28 mi (45 km)
  5. Lake Wilson, MN 31 mi (49 km)

Sources

* Hardiness zone 5a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 43.645, -95.5803.