U.S. Frost Dates by Weather Station

NOAA station USC00399232 · South Dakota

Frost Dates for White Lake, SD

NOAA weather station White Lake (USC00399232), South Dakota · elevation 1629 ft (497 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 350% chance of a frost after it
  • Typical first fall frostOctober 550% chance of a frost before it
  • Frost-free season153 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at White Lake, SDSpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 5 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 153 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 3First frost ~Oct 5Frost season at White Lake, SDSpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 5 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 153 days.JFMAMJJASONDLast frost ~May 3First frost ~Oct 5
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 17September 21
50% (typical)May 3October 5
90% (likely)April 20October 18
Frost-free season (32°F, 50% chance)
153 days
Hard frost (28°F), last in spring, 50% chance after
April 25
Hard frost (28°F), first in fall, 50% chance before
October 14

The last 15 years (2006–2020 normals)

Typical last frost May 4 (1 day later than the 30-year normal), typical first fall frost October 10 (5 days later). Frost-free season 158 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 White Lake: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 11, 30% May 7, 40% May 5, 50% May 3, 60% May 1, 70% April 29, 80% April 25, 90% April 20. Observed last spring frost in recent years: 2021 May 6, 2022 May 23, 2023 May 3, 2024 April 25, 2025 April 20, 2026 May 8.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 3Apr 202021: May 62022: May 232023: May 32024: April 252025: April 202026: May 8Fall at White Lake: chance of a frost before this dateFall, chance of a frost before the date: 10% September 21, 20% September 27, 30% September 30, 40% October 2, 50% October 5, 60% October 8, 70% October 11, 80% October 14, 90% October 18. Observed first fall frost in recent years: 2021 October 15, 2022 October 7, 2023 October 7, 2024 October 1, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 21Oct 5Oct 182021: October 152022: October 72023: October 72024: October 12025: October 22
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 15
2022May 23October 7
2023May 3October 7
2024April 25October 1
2025April 20October 22
2026May 8season not over yet

What these dates mean

The 153 days between the 50% dates in White Lake – May 3 and October 5 – define the period in which a light frost is equally likely to have occurred or not. For a gardener this median point marks the middle of the frost-risk window, not a frost event itself.

In spring the cautious date for setting out tender crops is May 17, when there is only a 10 % chance of a later light frost; planting on April 20 carries a 90 % chance and is a gamble. In fall the cautious date to finish harvesting tender crops is September 21, with only a 10 % chance that a light frost has already arrived, while October 18 represents a 90 % chance and a gamble.

A hard frost at 28 °F, shown by the median dates April 25 and October 14, matters more because it can kill plants that would survive a 32 °F light frost.

How to read the probabilities

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

  • Spring: "10% after May 17" 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 21" 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 White Lake, SDNumbered nearest stations: 1 — Academy, SD — 24 mi; 2 — Wessington Springs, SD — 27 mi; 3 — Chamberlain, SD — 32 mi; 4 — Pickstown, SD — 43 mi; 5 — Alexandria, SD — 44 mi.25 mi · 40 km1. Academy, SD — 24 mi12. Wessington Springs, SD — 27 mi23. Chamberlain, SD — 32 mi34. Pickstown, SD — 43 mi45. Alexandria, SD — 44 mi5
  1. Academy, SD 24 mi (38 km)
  2. Wessington Springs, SD 27 mi (44 km)
  3. Chamberlain, SD 32 mi (52 km)
  4. Pickstown, SD 43 mi (70 km)
  5. Alexandria, SD 44 mi (70 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: 43.6872, -98.6717.