U.S. Frost Dates by Weather Station

NOAA station USC00391049 · South Dakota

Frost Dates for Britton, SD

NOAA weather station Britton (USC00391049), South Dakota · elevation 1355 ft (413 m) · hardiness zone 4a*

  • Lower-risk planting dateafter May 27only 1 spring in 10 still has a frost later
  • Typical last frostMay 1350% chance of a frost after it
  • Typical first fall frostSeptember 2650% chance of a frost before it
  • Frost-free season135 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Britton, SDSpring: a frost after April 29 in 9 years out of 10, after May 13 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 14 in 1 year out of 10, before September 26 in half of the years, before October 7 in 9 years out of 10. Typical frost-free season: 135 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 13First frost ~Sep 26Frost season at Britton, SDSpring: a frost after April 29 in 9 years out of 10, after May 13 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 14 in 1 year out of 10, before September 26 in half of the years, before October 7 in 9 years out of 10. Typical frost-free season: 135 days.JFMAMJJASONDLast frost ~May 13First frost ~Sep 26
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 27September 14
50% (typical)May 13September 26
90% (likely)April 29October 7
Frost-free season (32°F, 50% chance)
135 days
Hard frost (28°F), last in spring, 50% chance after
May 2
Hard frost (28°F), first in fall, 50% chance before
October 3

The last 15 years (2006–2020 normals)

Typical last frost May 13 (same as the 30-year normal), typical first fall frost September 29 (3 days later). Frost-free season 138 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 Britton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 27, 20% May 22, 30% May 19, 40% May 15, 50% May 13, 60% May 10, 70% May 7, 80% May 3, 90% April 29. Observed last spring frost in recent years: 2021 May 11, 2022 April 28, 2023 May 3, 2024 April 25, 2025 May 4, 2026 May 8.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 27May 13Apr 292021: May 112022: April 282023: May 32024: April 252025: May 42026: May 8Fall at Britton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 14, 20% September 18, 30% September 21, 40% September 24, 50% September 26, 60% September 28, 70% September 30, 80% October 3, 90% October 7. Observed first fall frost in recent years: 2021 October 15, 2022 October 7, 2023 October 7, 2024 October 1, 2025 October 14.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 14Sep 26Oct 72021: October 152022: October 72023: October 72024: October 12025: October 14
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 15
2022April 28October 7
2023May 3October 7
2024April 25October 1
2025May 4October 14
2026May 8season not over yet

What these dates mean

May 27 is the cautious spring light-frost date for Britton, carrying only a 10 % chance that a frost will occur later. This low risk lets a gardener schedule the setting out of tender crops with confidence, knowing that most years the temperature will stay above 32 °F after that point.

The 50 % light-frost dates are May 13 in spring and September 26 in fall; on each of those days a frost is as likely as not. The cautious fall date is September 14, which has a 10 % chance of a frost arriving earlier, providing a reliable deadline for finishing tender-crop harvests. Hard frost reaches the 50 % level on May 2 and October 3, and because 28 °F can damage or kill many plants, it is a greater concern 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 27" 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 14" 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 Britton, SDNumbered nearest stations: 1 — Forman, ND — 18 mi; 2 — Columbia, SD — 27 mi; 3 — Waubay National Wild Life, SD — 32 mi; 4 — Webster, SD — 33 mi; 5 — Sisseton, SD — 35 mi.SDNDMN25 mi · 40 km1. Forman, ND — 18 mi12. Columbia, SD — 27 mi23. Waubay National Wild Life, SD — 32 mi34. Webster, SD — 33 mi45. Sisseton, SD — 35 mi5
  1. Forman, ND 18 mi (30 km)
  2. Columbia, SD 27 mi (44 km)
  3. Waubay National Wild Life, SD 32 mi (52 km)
  4. Webster, SD 33 mi (54 km)
  5. Sisseton, SD 35 mi (57 km)

Sources

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

Station coordinates: 45.7886, -97.7489.