U.S. Frost Dates by Weather Station

NOAA station USW00024025 · South Dakota

Frost Dates for Pierre, SD

NOAA weather station Pierre Regional Airport (USW00024025), South Dakota · elevation 1742 ft (531 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 21only 1 spring in 10 still has a frost later
  • Typical last frostMay 650% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season148 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Pierre, SDSpring: a frost after April 24 in 9 years out of 10, after May 6 in half of the years, after May 21 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: 148 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 6First frost ~Oct 3Frost season at Pierre, SDSpring: a frost after April 24 in 9 years out of 10, after May 6 in half of the years, after May 21 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: 148 days.JFMAMJJASONDLast frost ~May 6First 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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 21September 20
50% (typical)May 6October 3
90% (likely)April 24October 17
Frost-free season (32°F, 50% chance)
148 days
Hard frost (28°F), last in spring, 50% chance after
April 26
Hard frost (28°F), first in fall, 50% chance before
October 12

The last 15 years (2006–2020 normals)

Typical last frost May 8 (2 days later than the 30-year normal), typical first fall frost October 5 (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 Pierre: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 21, 20% May 16, 30% May 12, 40% May 9, 50% May 6, 60% May 4, 70% May 2, 80% April 29, 90% April 24. Observed last spring frost in recent years: 2021 May 11, 2022 May 22, 2023 May 2, 2024 May 3, 2025 April 29, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 21May 6Apr 242021: May 112022: May 222023: May 22024: May 32025: April 292026: May 20Fall at Pierre: 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 3, 60% October 6, 70% October 9, 80% October 13, 90% October 17. Observed first fall frost in recent years: 2021 October 20, 2022 October 6, 2023 October 7, 2024 October 14, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 20Oct 3Oct 172021: October 202022: October 62023: October 72024: October 142025: 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 11October 20
2022May 22October 6
2023May 2October 7
2024May 3October 14
2025April 29October 13
2026May 20season not over yet

What these dates mean

May 21 is the cautious spring date in Pierre, carrying a 10% chance of a light frost later and allowing a gardener to set out tender crops with relatively low risk. The matching cautious fall date is September 20, which has a 10% chance of a light frost earlier and guides the latest time to finish harvesting tender crops.

The 50% date is May 6, at which point there is a 50% chance of a light frost later than this date. The 50% date is October 3, at which point there is a 50% chance of a light frost earlier than this date. The hard-frost 50% dates are April 26 in spring and October 12 in fall; a hard frost can damage plants more severely than a light frost because it reaches lower temperatures.

How to read the probabilities

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

  • Spring: "10% after May 21" 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 Pierre, SDNumbered nearest stations: 1 — Onida, SD — 25 mi; 2 — Kennebec, SD — 39 mi; 3 — Murdo, SD — 40 mi; 4 — Highmore, SD — 42 mi; 5 — Miller, SD — 65 mi.SD25 mi · 40 km1. Onida, SD — 25 mi12. Kennebec, SD — 39 mi23. Murdo, SD — 40 mi34. Highmore, SD — 42 mi45. Miller, SD — 65 mi5
  1. Onida, SD 25 mi (41 km)
  2. Kennebec, SD 39 mi (63 km)
  3. Murdo, SD 40 mi (64 km)
  4. Highmore, SD 42 mi (68 km)
  5. Miller, SD 65 mi (105 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: 44.3814, -100.2856.