U.S. Frost Dates by Weather Station

NOAA station USW00094911 · South Dakota

Frost Dates for Yankton, SD

NOAA weather station Yankton 2 E (USW00094911), South Dakota · elevation 1180 ft (360 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 10only 1 spring in 10 still has a frost later
  • Typical last frostApril 2750% chance of a frost after it
  • Typical first fall frostOctober 1150% chance of a frost before it
  • Frost-free season164 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Yankton, SDSpring: a frost after April 13 in 9 years out of 10, after April 27 in half of the years, after May 10 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 11 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 164 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 27First frost ~Oct 11Frost season at Yankton, SDSpring: a frost after April 13 in 9 years out of 10, after April 27 in half of the years, after May 10 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 11 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 164 days.JFMAMJJASONDLast frost ~Apr 27First frost ~Oct 11
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 10September 27
50% (typical)April 27October 11
90% (likely)April 13October 23
Frost-free season (32°F, 50% chance)
164 days
Hard frost (28°F), last in spring, 50% chance after
April 18
Hard frost (28°F), first in fall, 50% chance before
October 21

The last 15 years (2006–2020 normals)

Typical last frost April 26 (1 day earlier than the 30-year normal), typical first fall frost October 13 (2 days later). Frost-free season 170 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 Yankton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 10, 20% May 6, 30% May 2, 40% April 30, 50% April 27, 60% April 24, 70% April 21, 80% April 18, 90% April 13. Observed last spring frost in recent years: 2021 May 6, 2022 May 22, 2023 May 2, 2024 April 21, 2025 April 21, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 10Apr 27Apr 132021: May 62022: May 222023: May 22024: April 212025: April 212026: May 7Fall at Yankton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 27, 20% October 1, 30% October 4, 40% October 8, 50% October 11, 60% October 14, 70% October 17, 80% October 19, 90% October 23. Observed first fall frost in recent years: 2021 October 22, 2022 October 7, 2023 October 7, 2024 October 14.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 11Oct 232021: October 222022: October 72023: October 72024: October 14
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 6October 22
2022May 22October 7
2023May 2October 7
2024April 21October 14
2025April 21incomplete record
2026May 7season not over yet

What these dates mean

September 27 is the cautious fall date for finishing the harvest of tender crops in Yankton, when there is only a 10 % chance that a light frost has arrived earlier.

The 50% light-frost dates are April 27 in spring and October 11 in fall; they represent the point at which a frost is equally likely to occur later (spring) or earlier (fall). For a low-risk schedule, gardeners should aim to set out tender crops after the cautious spring date of May 10, which carries a 10 % chance of a later frost, and to pull back by the cautious fall date of September 27.

Hard frost, defined at 28 °F, is more damaging than a light frost at 32 °F, so the median hard-frost dates of April 18 and October 21 are useful reference points for protecting vulnerable 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 10" 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 27" 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 Yankton, SDNumbered nearest stations: 1 — Crofton, NE — 12 mi; 2 — Hartington, NE — 19 mi; 3 — Vermillion, SD — 24 mi; 4 — Centerville, SD — 26 mi; 5 — Tyndall, SD — 27 mi.SDNEIA25 mi · 40 km1. Crofton, NE — 12 mi12. Hartington, NE — 19 mi23. Vermillion, SD — 24 mi34. Centerville, SD — 26 mi45. Tyndall, SD — 27 mi5
  1. Crofton, NE 12 mi (19 km)
  2. Hartington, NE 19 mi (30 km)
  3. Vermillion, SD 24 mi (38 km)
  4. Centerville, SD 26 mi (42 km)
  5. Tyndall, SD 27 mi (43 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: 42.8783, -97.3633.