U.S. Frost Dates by Weather Station

NOAA station USW00014936 · South Dakota

Frost Dates for Huron, SD

NOAA weather station Huron Regional Airport (USW00014936), South Dakota · elevation 1280 ft (390 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 20only 1 spring in 10 still has a frost later
  • Typical last frostMay 650% chance of a frost after it
  • Typical first fall frostOctober 250% chance of a frost before it
  • Frost-free season146 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Huron, SDSpring: a frost after April 23 in 9 years out of 10, after May 6 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 2 in half of the years, before October 14 in 9 years out of 10. Typical frost-free season: 146 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 6First frost ~Oct 2Frost season at Huron, SDSpring: a frost after April 23 in 9 years out of 10, after May 6 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 2 in half of the years, before October 14 in 9 years out of 10. Typical frost-free season: 146 days.JFMAMJJASONDLast frost ~May 6First frost ~Oct 2
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 20September 19
50% (typical)May 6October 2
90% (likely)April 23October 14
Frost-free season (32°F, 50% chance)
146 days
Hard frost (28°F), last in spring, 50% chance after
April 27
Hard frost (28°F), first in fall, 50% chance before
October 8

The last 15 years (2006–2020 normals)

Typical last frost May 6 (same as the 30-year normal), typical first fall frost October 4 (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 Huron: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 20, 20% May 15, 30% May 12, 40% May 9, 50% May 6, 60% May 4, 70% May 1, 80% April 28, 90% April 23. Observed last spring frost in recent years: 2021 May 11, 2022 May 2, 2023 May 2, 2024 April 24, 2025 April 29, 2026 May 6.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 20May 6Apr 232021: May 112022: May 22023: May 22024: April 242025: April 292026: May 6Fall at Huron: chance of a frost before this dateFall, chance of a frost before the date: 10% September 19, 20% September 23, 30% September 27, 40% September 30, 50% October 2, 60% October 4, 70% October 7, 80% October 10, 90% October 14. Observed first fall frost in recent years: 2021 October 16, 2022 October 6, 2023 October 6, 2024 October 4, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 19Oct 2Oct 142021: October 162022: October 62023: October 62024: October 42025: 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 16
2022May 2October 6
2023May 2October 6
2024April 24October 4
2025April 29October 13
2026May 6season not over yet

What these dates mean

In Huron, the cautious spring date is May 20, when there is only a 10% chance of a light frost later, allowing a gardener to set out tender crops with low risk. The 50% date of May 6 marks the point where a light frost is equally likely to occur later, providing a reference for average risk. The median hard-frost date of April 27 indicates an even chance of temperatures reaching 28 °F.

For fall, the cautious date is September 19, when there is a 10% chance of a light frost earlier, giving a gardener a reliable deadline to finish harvesting tender crops. October 2 is the 50% date for a light frost, showing even odds. The median hard-frost date of October 8 signals an even chance of 28 °F. A hard frost at 28 °F can damage plants that survive a 32 °F light frost, making it a more critical threshold.

How to read the probabilities

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

  • Spring: "10% after May 20" 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 19" 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 Huron, SDNumbered nearest stations: 1 — Wessington Springs, SD — 28 mi; 2 — De Smet, SD — 33 mi; 3 — Miller, SD — 38 mi; 4 — White Lake, SD — 54 mi; 5 — Mellette, SD — 55 mi.50 mi · 80 km1. Wessington Springs, SD — 28 mi12. De Smet, SD — 33 mi23. Miller, SD — 38 mi34. White Lake, SD — 54 mi45. Mellette, SD — 55 mi5
  1. Wessington Springs, SD 28 mi (45 km)
  2. De Smet, SD 33 mi (54 km)
  3. Miller, SD 38 mi (62 km)
  4. White Lake, SD 54 mi (87 km)
  5. Mellette, SD 55 mi (89 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: 44.3981, -98.2231.