U.S. Frost Dates by Weather Station

NOAA station USC00397742 · South Dakota

Frost Dates for Sisseton, SD

NOAA weather station Sisseton (USC00397742), South Dakota · elevation 1209 ft (369 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 450% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season151 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Sisseton, SDSpring: a frost after April 21 in 9 years out of 10, after May 4 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 3 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 151 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 4First frost ~Oct 3Frost season at Sisseton, SDSpring: a frost after April 21 in 9 years out of 10, after May 4 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 3 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 151 days.JFMAMJJASONDLast frost ~May 4First frost ~Oct 3
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 17September 22
50% (typical)May 4October 3
90% (likely)April 21October 17
Frost-free season (32°F, 50% chance)
151 days
Hard frost (28°F), last in spring, 50% chance after
April 26
Hard frost (28°F), first in fall, 50% chance before
October 14

The last 15 years (2006–2020 normals)

Typical last frost May 5 (1 day later than the 30-year normal), typical first fall frost October 6 (3 days later). Frost-free season 152 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 Sisseton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 12, 30% May 8, 40% May 6, 50% May 4, 60% May 1, 70% April 29, 80% April 26, 90% April 21. Observed last spring frost in recent years: 2021 May 11, 2022 April 28, 2023 April 26, 2024 April 30, 2025 April 29, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 4Apr 212021: May 112022: April 282023: April 262024: April 302025: April 292026: May 20Fall at Sisseton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 22, 20% September 26, 30% September 29, 40% October 1, 50% October 3, 60% October 5, 70% October 8, 80% October 12, 90% October 17. Observed first fall frost in recent years: 2021 October 21, 2022 September 28, 2023 October 7, 2024 October 14, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 22Oct 3Oct 172021: October 212022: September 282023: October 72024: October 142025: October 8
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 21
2022April 28September 28
2023April 26October 7
2024April 30October 14
2025April 29October 8
2026May 20season not over yet

What these dates mean

The 151 days between the 32 °F 50% dates in Sisseton define the median window in which light-frost risk shifts from more likely to less likely. The 50% dates, May 4 in spring and October 3 in fall, simply mark the point where a light frost has an even chance of occurring; they are not themselves frost dates.

For a cautious approach, tender crops should be set out after the spring cautious date of May 17, when there is only a 10 % chance of a later light frost, and harvested before the fall cautious date of September 22, which carries only a 10 % chance that a light frost has already arrived.

Hard frost at 28 °F is more consequential than a light frost at 32 °F because the lower temperature can cause more severe damage to plant tissue, and the median hard-frost dates for Sisseton are April 26 in spring and October 14 in fall.

How to read the probabilities

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

  • Spring: "10% after May 17" 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 22" 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 Sisseton, SDNumbered nearest stations: 1 — Browns Valley, MN — 11 mi; 2 — Victor, SD — 20 mi; 3 — Waubay National Wild Life, SD — 22 mi; 4 — Summit, SD — 25 mi; 5 — Wheaton, MN — 28 mi.SDMNND25 mi · 40 km1. Browns Valley, MN — 11 mi12. Victor, SD — 20 mi23. Waubay National Wild Life, SD — 22 mi34. Summit, SD — 25 mi45. Wheaton, MN — 28 mi5
  1. Browns Valley, MN 11 mi (18 km)
  2. Victor, SD 20 mi (33 km)
  3. Waubay National Wild Life, SD 22 mi (35 km)
  4. Summit, SD 25 mi (40 km)
  5. Wheaton, MN 28 mi (44 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: 45.6656, -97.0394.