U.S. Frost Dates by Weather Station

NOAA station USC00399070 · South Dakota

Frost Dates for Wessington Springs, SD

NOAA weather station Wessington Springs (USC00399070), South Dakota · elevation 1715 ft (523 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 14only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 850% chance of a frost before it
  • Frost-free season157 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Wessington Springs, SDSpring: a frost after April 20 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 8 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 157 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 8Frost season at Wessington Springs, SDSpring: a frost after April 20 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 8 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 157 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 8
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 14September 26
50% (typical)May 2October 8
90% (likely)April 20October 20
Frost-free season (32°F, 50% chance)
157 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 2 (same as the 30-year normal), typical first fall frost October 13 (5 days later). Frost-free season 163 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 Wessington Springs: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 14, 20% May 9, 30% May 6, 40% May 4, 50% May 2, 60% April 30, 70% April 27, 80% April 24, 90% April 20. Observed last spring frost in recent years: 2021 May 7, 2022 May 21, 2023 April 25, 2024 April 22, 2025 April 20, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1May 14May 2Apr 202021: May 72022: May 212023: April 252024: April 222025: April 202026: May 7Fall at Wessington Springs: chance of a frost before this dateFall, chance of a frost before the date: 10% September 26, 20% September 30, 30% October 2, 40% October 5, 50% October 8, 60% October 10, 70% October 13, 80% October 16, 90% October 20. Observed first fall frost in recent years: 2021 October 17, 2022 October 6, 2023 October 7, 2024 October 15, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 26Oct 8Oct 202021: October 172022: October 62023: October 72024: October 152025: 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 7October 17
2022May 21October 6
2023April 25October 7
2024April 22October 15
2025April 20October 13
2026May 7season not over yet

What these dates mean

May 14 is the cautious spring date, giving a gardener the confidence to set out tender crops because only a 10% chance of a light frost remains after that day. The median spring light-frost date is May 2; at that point there is a 50% chance of a frost later, while the earlier April 20 date carries a 90% chance and is a gamble for tender crops.

For light frost, the median fall date is October 8, meaning a 50% chance of a frost earlier, and the cautious fall date is September 26, when there is just a 10% chance that a light frost has arrived, allowing the final harvest of tender crops. The later October 20 date has a 90% chance and is risky to rely on.

The hard-frost median dates are April 23 and October 15; a hard frost at 28°F can damage plants more severely than a light frost at 32°F, so these dates are important reference points.

How to read the probabilities

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

  • Spring: "10% after May 14" 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 26" 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 Wessington Springs, SDNumbered nearest stations: 1 — White Lake, SD — 27 mi; 2 — Huron, SD — 28 mi; 3 — Miller, SD — 37 mi; 4 — Chamberlain, SD — 44 mi; 5 — Academy, SD — 47 mi.25 mi · 40 km1. White Lake, SD — 27 mi12. Huron, SD — 28 mi23. Miller, SD — 37 mi34. Chamberlain, SD — 44 mi45. Academy, SD — 47 mi5
  1. White Lake, SD 27 mi (44 km)
  2. Huron, SD 28 mi (45 km)
  3. Miller, SD 37 mi (59 km)
  4. Chamberlain, SD 44 mi (70 km)
  5. Academy, SD 47 mi (76 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: 44.0756, -98.5706.