U.S. Frost Dates by Weather Station

NOAA station USC00398622 · South Dakota

Frost Dates for Vermillion, SD

NOAA weather station Vermillion 2 SE (USC00398622), South Dakota · elevation 1137 ft (347 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 16only 1 spring in 10 still has a frost later
  • Typical last frostMay 350% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season153 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Vermillion, SDSpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 16 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 3 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 153 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 3First frost ~Oct 3Frost season at Vermillion, SDSpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 16 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 3 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 153 days.JFMAMJJASONDLast frost ~May 3First frost ~Oct 3
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 16September 20
50% (typical)May 3October 3
90% (likely)April 20October 17
Frost-free season (32°F, 50% chance)
153 days
Hard frost (28°F), last in spring, 50% chance after
April 24
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 2 (1 day earlier than the 30-year normal), typical first fall frost October 6 (3 days later). Frost-free season 155 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 Vermillion: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 16, 20% May 12, 30% May 9, 40% May 5, 50% May 3, 60% April 30, 70% April 28, 80% April 25, 90% April 20. Observed last spring frost in recent years: 2021 May 11, 2022 May 23, 2023 May 2, 2024 April 21, 2025 April 21, 2026 May 6.Spring: last frostChance of a frost after this date10%50%90%May 1May 16May 3Apr 202021: May 112022: May 232023: May 22024: April 212025: April 212026: May 6Fall at Vermillion: 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 3, 60% October 6, 70% October 9, 80% October 13, 90% October 17. Observed first fall frost in recent years: 2021 October 16, 2022 October 7, 2023 October 7, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 20Oct 3Oct 172021: October 162022: October 72023: October 72025: 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 16
2022May 23October 7
2023May 2October 7
2024April 21incomplete record
2025April 21October 22
2026May 6season not over yet

What these dates mean

The 153 days between the 50% dates in Vermillion, May 3 and October 3, set the median window for light-frost risk. The 50% date is May 3, marking an even odds point for a light frost later in spring, while the 50% date is October 3, marking an even odds point for a light frost earlier in fall. These dates are not frost dates; they simply split the historical record into equal probability halves.

For gardeners taking a cautious plan, the spring light-frost date is May 16, when there is only a 10 % chance of a frost later, making it the recommended day to set out tender crops. In fall, the cautious date is September 20, with a 10 % chance of a frost earlier, signaling the safest time to finish harvesting tender crops.

Hard frost at 28 °F, as indicated by the median dates April 24 and October 15, can cause damage that a 32 °F light frost does not, so it represents a higher risk for plants.

How to read the probabilities

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

  • Spring: "10% after May 16" 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 Vermillion, SDNumbered nearest stations: 1 — Centerville, SD — 19 mi; 2 — Hartington, NE — 20 mi; 3 — Yankton, SD — 24 mi; 4 — Hawarden, IA — 28 mi; 5 — Crofton, NE — 29 mi.SDIA25 mi · 40 km1. Centerville, SD — 19 mi12. Hartington, NE — 20 mi23. Yankton, SD — 24 mi34. Hawarden, IA — 28 mi45. Crofton, NE — 29 mi5
  1. Centerville, SD 19 mi (31 km)
  2. Hartington, NE 20 mi (32 km)
  3. Yankton, SD 24 mi (38 km)
  4. Hawarden, IA 28 mi (44 km)
  5. Crofton, NE 29 mi (47 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: 42.7625, -96.9194.