U.S. Frost Dates by Weather Station

NOAA station USC00398472 · South Dakota

Frost Dates for Tyndall, SD

NOAA weather station Tyndall (USC00398472), South Dakota · elevation 1420 ft (433 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 14only 1 spring in 10 still has a frost later
  • Typical last frostMay 150% chance of a frost after it
  • Typical first fall frostOctober 750% chance of a frost before it
  • Frost-free season158 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Tyndall, SDSpring: a frost after April 18 in 9 years out of 10, after May 1 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 24 in 1 year out of 10, before October 7 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 158 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 1First frost ~Oct 7Frost season at Tyndall, SDSpring: a frost after April 18 in 9 years out of 10, after May 1 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 24 in 1 year out of 10, before October 7 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 158 days.JFMAMJJASONDLast frost ~May 1First frost ~Oct 7
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 14September 24
50% (typical)May 1October 7
90% (likely)April 18October 20
Frost-free season (32°F, 50% chance)
158 days
Hard frost (28°F), last in spring, 50% chance after
April 21
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost May 1 (same as the 30-year normal), typical first fall frost October 12 (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 Tyndall: 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 3, 50% May 1, 60% April 29, 70% April 26, 80% April 23, 90% April 18. Observed last spring frost in recent years: 2021 May 11, 2022 May 22, 2023 May 2, 2024 April 21, 2025 April 22, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1May 14May 1Apr 182021: May 112022: May 222023: May 22024: April 212025: April 222026: May 7Fall at Tyndall: chance of a frost before this dateFall, chance of a frost before the date: 10% September 24, 20% September 28, 30% October 1, 40% October 4, 50% October 7, 60% October 10, 70% October 13, 80% October 16, 90% October 20. Observed first fall frost in recent years: 2021 October 16, 2022 October 7, 2023 October 7, 2024 October 14, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 24Oct 7Oct 202021: October 162022: October 72023: October 72024: October 142025: 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 11October 16
2022May 22October 7
2023May 2October 7
2024April 21October 14
2025April 22October 22
2026May 7season not over yet

What these dates mean

Setting out tender crops on the early spring date, April 18, is a gamble because there is a 90 % chance of a light frost later than that date. Gardeners who prefer a lower risk wait until the cautious spring date, May 14, when only a 10 % chance of a light frost remains.

The 50 % dates mark the point at which a light frost is equally likely to have occurred or not; May 1 and October 7 are those median dates for spring and fall. The cautious fall date for finishing tender crops is September 24, carrying a 10 % chance of an earlier light frost, while October 20 is a gamble with a 90 % chance of an earlier frost.

A hard frost at 28 °F, indicated by the median dates April 21 and October 17, can harm plants that would survive a light frost at 32 °F, making it a more serious threat.

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 24" 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 Tyndall, SDNumbered nearest stations: 1 — Menno, SD — 23 mi; 2 — Crofton, NE — 26 mi; 3 — Yankton, SD — 27 mi; 4 — Lynch, NE — 32 mi; 5 — Pickstown, SD — 34 mi.SDNE25 mi · 40 km1. Menno, SD — 23 mi12. Crofton, NE — 26 mi23. Yankton, SD — 27 mi34. Lynch, NE — 32 mi45. Pickstown, SD — 34 mi5
  1. Menno, SD 23 mi (36 km)
  2. Crofton, NE 26 mi (42 km)
  3. Yankton, SD 27 mi (43 km)
  4. Lynch, NE 32 mi (52 km)
  5. Pickstown, SD 34 mi (55 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: 42.9917, -97.8703.