U.S. Frost Dates by Weather Station

NOAA station USC00399347 · South Dakota

Frost Dates for Wind Cave, SD

NOAA weather station Wind Cave (USC00399347), South Dakota · elevation 4155 ft (1266 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 30only 1 spring in 10 still has a frost later
  • Typical last frostMay 1550% chance of a frost after it
  • Typical first fall frostSeptember 2950% chance of a frost before it
  • Frost-free season133 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Wind Cave, SDSpring: a frost after May 4 in 9 years out of 10, after May 15 in half of the years, after May 30 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 133 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 15First frost ~Sep 29Frost season at Wind Cave, SDSpring: a frost after May 4 in 9 years out of 10, after May 15 in half of the years, after May 30 in 1 year out of 10. Fall: the first frost comes before September 13 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 133 days.JFMAMJJASONDLast frost ~May 15First frost ~Sep 29
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 30September 13
50% (typical)May 15September 29
90% (likely)May 4October 11
Frost-free season (32°F, 50% chance)
133 days
Hard frost (28°F), last in spring, 50% chance after
May 5
Hard frost (28°F), first in fall, 50% chance before
October 6

The last 15 years (2006–2020 normals)

Typical last frost May 15 (same as the 30-year normal), typical first fall frost September 30 (1 day later). Frost-free season 135 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 Wind Cave: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 30, 20% May 25, 30% May 21, 40% May 18, 50% May 15, 60% May 13, 70% May 11, 80% May 8, 90% May 4. Observed last spring frost in recent years: 2021 May 12, 2022 May 25, 2023 May 2, 2024 May 4, 2025 April 29, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 30May 15May 42021: May 122022: May 252023: May 22024: May 42025: April 292026: May 20Fall at Wind Cave: chance of a frost before this dateFall, chance of a frost before the date: 10% September 13, 20% September 20, 30% September 23, 40% September 26, 50% September 29, 60% October 1, 70% October 3, 80% October 6, 90% October 11. Observed first fall frost in recent years: 2021 October 14, 2022 October 8, 2023 October 7, 2024 October 13, 2025 October 7.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 13Sep 29Oct 112021: October 142022: October 82023: October 72024: October 132025: October 7
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 14
2022May 25October 8
2023May 2October 7
2024May 4October 13
2025April 29October 7
2026May 20season not over yet

What these dates mean

The cautious fall date for finishing the harvest in Wind Cave is September 13, when there is only a 10 % chance a light frost has arrived.

For tender crops in spring the cautious date is May 30, the point at which a light frost later than that day has only a 10 % chance; planting on May 4 carries a 90 % chance of a frost and is a gamble. The 50 % date is May 15, marking an even chance of a light frost later than this date, while the fall 50 % date is September 29, when a light frost earlier than that day is equally likely.

The 50 % hard-frost dates are May 5 and October 6; a hard frost at 28 °F can damage plant tissue that survives a light frost at 32 °F, making it the more critical temperature threshold.

How to read the probabilities

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

  • Spring: "10% after May 30" 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 13" 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 Wind Cave, SDNumbered nearest stations: 1 — Hot Springs, SD — 8 mi; 2 — Oral, SD — 15 mi; 3 — Custer, SD — 16 mi; 4 — Mount Rushmore National Memorial, SD — 22 mi; 5 — Hill City, SD — 26 mi.SDWYNE25 mi · 40 km1. Hot Springs, SD — 8 mi12. Oral, SD — 15 mi23. Custer, SD — 16 mi34. Mount Rushmore National Memorial, SD — 22 mi45. Hill City, SD — 26 mi5
  1. Hot Springs, SD 8 mi (13 km)
  2. Oral, SD 15 mi (24 km)
  3. Custer, SD 16 mi (27 km)
  4. Mount Rushmore National Memorial, SD 22 mi (36 km)
  5. Hill City, SD 26 mi (43 km)

Sources

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

Station coordinates: 43.5561, -103.4794.