U.S. Frost Dates by Weather Station

NOAA station USC00392446 · South Dakota

Frost Dates for Dupree 15 SSE, SD

NOAA weather station Dupree 15 SSE (USC00392446), South Dakota · elevation 2100 ft (640 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 20only 1 spring in 10 still has a frost later
  • Typical last frostMay 650% chance of a frost after it
  • Typical first fall frostOctober 250% chance of a frost before it
  • Frost-free season148 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Dupree 15 SSE, SDSpring: a frost after April 24 in 9 years out of 10, after May 6 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 2 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 148 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 6First frost ~Oct 2Frost season at Dupree 15 SSE, SDSpring: a frost after April 24 in 9 years out of 10, after May 6 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 2 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 148 days.JFMAMJJASONDLast frost ~May 6First frost ~Oct 2
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 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 20September 20
50% (typical)May 6October 2
90% (likely)April 24October 16
Frost-free season (32°F, 50% chance)
148 days
Hard frost (28°F), last in spring, 50% chance after
April 27
Hard frost (28°F), first in fall, 50% chance before
October 11

The last 15 years (2006–2020 normals)

Typical last frost May 6 (same as the 30-year normal), typical first fall frost October 4 (2 days later). Frost-free season 149 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 Dupree 15 SSE: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 20, 20% May 16, 30% May 12, 40% May 9, 50% May 6, 60% May 4, 70% May 2, 80% April 28, 90% April 24. Observed last spring frost in recent years: 2021 May 10, 2022 May 22, 2023 May 2, 2024 May 4, 2025 April 29, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 20May 6Apr 242021: May 102022: May 222023: May 22024: May 42025: April 292026: May 7Fall at Dupree 15 SSE: chance of a frost before this dateFall, chance of a frost before the date: 10% September 20, 20% September 24, 30% September 28, 40% September 30, 50% October 2, 60% October 5, 70% October 7, 80% October 11, 90% October 16. Observed first fall frost in recent years: 2021 October 14, 2022 October 7, 2023 October 6, 2024 October 1, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 20Oct 2Oct 162021: October 142022: October 72023: October 62024: October 12025: October 13
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 10October 14
2022May 22October 7
2023May 2October 6
2024May 4October 1
2025April 29October 13
2026May 7season not over yet

What these dates mean

The 148 days between the 50% dates in Dupree 15 SSE mark the span when a light frost (32 °F) is less likely than not. The 50% spring date is May 6 and the 50% fall date is October 2; each represents an even chance of a frost occurring after or before that point respectively.

For a cautious plan, gardeners should wait until May 20 to set out tender crops, because only a 10% chance of a frost later than that date remains. In the autumn, September 20 serves as the cautious date to finish harvesting tender crops, with only a 10% chance that a frost has arrived earlier.

A hard frost at 28 °F, whose 50% dates are April 27 in spring and October 11 in fall, can damage plants that would survive a light frost, making it a more serious threat.

How to read the probabilities

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

  • Spring: "10% after May 20" 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 Dupree 15 SSE, SDNumbered nearest stations: 1 — Dupree, SD — 14 mi; 2 — Milesville, SD — 25 mi; 3 — Glad Valley, SD — 41 mi; 4 — Timber Lake, SD — 43 mi; 5 — Maurine, SD — 54 mi.SD25 mi · 40 km1. Dupree, SD — 14 mi12. Milesville, SD — 25 mi23. Glad Valley, SD — 41 mi34. Timber Lake, SD — 43 mi45. Maurine, SD — 54 mi5
  1. Dupree, SD 14 mi (23 km)
  2. Milesville, SD 25 mi (41 km)
  3. Glad Valley, SD 41 mi (65 km)
  4. Timber Lake, SD 43 mi (70 km)
  5. Maurine, SD 54 mi (87 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: 44.8658, -101.4672.