U.S. Frost Dates by Weather Station

NOAA station USC00398980 · South Dakota

Frost Dates for Waubay National Wild Life, SD

NOAA weather station Waubay National Wild Life (USC00398980), South Dakota · elevation 1827 ft (557 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 12only 1 spring in 10 still has a frost later
  • Typical last frostMay 150% chance of a frost after it
  • Typical first fall frostOctober 1250% chance of a frost before it
  • Frost-free season164 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Waubay National Wild Life, SDSpring: a frost after April 17 in 9 years out of 10, after May 1 in half of the years, after May 12 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 12 in half of the years, before October 26 in 9 years out of 10. Typical frost-free season: 164 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 1First frost ~Oct 12Frost season at Waubay National Wild Life, SDSpring: a frost after April 17 in 9 years out of 10, after May 1 in half of the years, after May 12 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 12 in half of the years, before October 26 in 9 years out of 10. Typical frost-free season: 164 days.JFMAMJJASONDLast frost ~May 1First frost ~Oct 12
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 12September 30
50% (typical)May 1October 12
90% (likely)April 17October 26
Frost-free season (32°F, 50% chance)
164 days
Hard frost (28°F), last in spring, 50% chance after
April 21
Hard frost (28°F), first in fall, 50% chance before
October 21

The last 15 years (2006–2020 normals)

Typical last frost May 3 (2 days later than the 30-year normal), typical first fall frost October 16 (4 days later). Frost-free season 166 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 Waubay National Wild Life: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 12, 20% May 9, 30% May 6, 40% May 3, 50% May 1, 60% April 29, 70% April 26, 80% April 22, 90% April 17. Observed last spring frost in recent years: 2021 May 4, 2022 May 3, 2023 May 3, 2024 April 20, 2025 April 28.Spring: last frostChance of a frost after this date10%50%90%May 1May 12May 1Apr 172021: May 42022: May 32023: May 32024: April 202025: April 28Fall at Waubay National Wild Life: chance of a frost before this dateFall, chance of a frost before the date: 10% September 30, 20% October 3, 30% October 7, 40% October 10, 50% October 12, 60% October 15, 70% October 18, 80% October 21, 90% October 26. Observed first fall frost in recent years: 2021 October 21, 2022 October 7, 2023 October 27, 2024 October 31.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 30Oct 12Oct 262021: October 212022: October 72023: October 272024: October 31
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 4October 21
2022May 3October 7
2023May 3October 27
2024April 20October 31
2025April 28incomplete record
2026incomplete recordseason not over yet

What these dates mean

The cautious fall date in Waubay National Wild Life for finishing the harvest is September 30. That date carries only a 10% chance that a light frost has already arrived, making it the low-risk point to end tender-crop production.

In spring, the cautious date for setting out tender crops is May 12, a 10% chance of a light frost later than that day. The 50% date is May 1, indicating an even chance of a light frost later than that date. In fall, the 50% date is October 12, indicating an even chance of a light frost earlier than that date, while the cautious date to finish harvesting is September 30.

Hard frost at 28 °F, marked by the 50% dates of April 21 in spring and October 21 in fall, can damage plants more severely than a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after May 12" 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 30" 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 Waubay National Wild Life, SDNumbered nearest stations: 1 — Webster, SD — 11 mi; 2 — Summit, SD — 15 mi; 3 — Sisseton, SD — 22 mi; 4 — Browns Valley, MN — 27 mi; 5 — Britton, SD — 32 mi.MNND25 mi · 40 km1. Webster, SD — 11 mi12. Summit, SD — 15 mi23. Sisseton, SD — 22 mi34. Browns Valley, MN — 27 mi45. Britton, SD — 32 mi5
  1. Webster, SD 11 mi (18 km)
  2. Summit, SD 15 mi (25 km)
  3. Sisseton, SD 22 mi (35 km)
  4. Browns Valley, MN 27 mi (43 km)
  5. Britton, SD 32 mi (52 km)

Sources

* Hardiness zone 4b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 45.4247, -97.3269.