U.S. Frost Dates by Weather Station

NOAA station USC00394007 · South Dakota

Frost Dates for Hot Springs, SD

NOAA weather station Hot Springs (USC00394007), South Dakota · elevation 3560 ft (1085 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 31only 1 spring in 10 still has a frost later
  • Typical last frostMay 1650% chance of a frost after it
  • Typical first fall frostSeptember 2750% chance of a frost before it
  • Frost-free season133 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Hot Springs, SDSpring: a frost after May 4 in 9 years out of 10, after May 16 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 12 in 1 year out of 10, before September 27 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 133 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 16First frost ~Sep 27Frost season at Hot Springs, SDSpring: a frost after May 4 in 9 years out of 10, after May 16 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 12 in 1 year out of 10, before September 27 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 133 days.JFMAMJJASONDLast frost ~May 16First frost ~Sep 27
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 31September 12
50% (typical)May 16September 27
90% (likely)May 4October 9
Frost-free season (32°F, 50% chance)
133 days
Hard frost (28°F), last in spring, 50% chance after
May 5
Hard frost (28°F), first in fall, 50% chance before
October 7

The last 15 years (2006–2020 normals)

Typical last frost May 16 (same as the 30-year normal), typical first fall frost September 29 (2 days later). Frost-free season 132 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 Hot Springs: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 31, 20% May 26, 30% May 22, 40% May 19, 50% May 16, 60% May 13, 70% May 10, 80% May 8, 90% May 4. Observed last spring frost in recent years: 2021 May 15, 2022 May 27, 2024 May 5, 2025 May 22, 2026 May 21.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 31May 16May 42021: May 152022: May 272024: May 52025: May 222026: May 21Fall at Hot Springs: chance of a frost before this dateFall, chance of a frost before the date: 10% September 12, 20% September 18, 30% September 22, 40% September 25, 50% September 27, 60% September 30, 70% October 2, 80% October 5, 90% October 9. Observed first fall frost in recent years: 2021 October 11, 2022 October 8, 2024 October 1, 2025 September 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 12Sep 27Oct 92021: October 112022: October 82024: October 12025: September 6
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 15October 11
2022May 27October 8
2023no datano data
2024May 5October 1
2025May 22September 6
2026May 21season not over yet

What these dates mean

Setting out tender crops on the early spring date, May 4, carries a 90% chance of a light frost and is therefore a gamble for Hot Springs gardeners. The cautious plan waits until May 31, when only a 10% chance of a later frost remains. The 50% date, May 16, simply marks the point at which the odds of a frost later than that day are even, serving as a reference rather than a frost cutoff.

In the fall, the cautious date to finish harvesting tender crops is September 12, with only a 10% chance that a frost has already arrived. Counting on crops to survive until October 9 involves a 90% chance of an earlier frost and is a gamble. The 50% date, September 27, indicates equal odds of a frost occurring earlier. Hard-frost median dates are May 5 and October 7, and a hard frost at 28 °F matters more because it can kill plants that survive the milder 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 31" 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 12" 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 Hot Springs, SDNumbered nearest stations: 1 — Wind Cave, SD — 8 mi; 2 — Oral, SD — 11 mi; 3 — Oelrichs, SD — 21 mi; 4 — Custer, SD — 24 mi; 5 — Mount Rushmore National Memorial, SD — 30 mi.SDWYNE25 mi · 40 km1. Wind Cave, SD — 8 mi12. Oral, SD — 11 mi23. Oelrichs, SD — 21 mi34. Custer, SD — 24 mi45. Mount Rushmore National Memorial, SD — 30 mi5
  1. Wind Cave, SD 8 mi (13 km)
  2. Oral, SD 11 mi (17 km)
  3. Oelrichs, SD 21 mi (34 km)
  4. Custer, SD 24 mi (39 km)
  5. Mount Rushmore National Memorial, SD 30 mi (49 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: 43.4378, -103.4739.