U.S. Frost Dates by Weather Station

NOAA station USC00396292 · South Dakota

Frost Dates for Onida, SD

NOAA weather station Onida 4 NW (USC00396292), South Dakota · elevation 1851 ft (564 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 22only 1 spring in 10 still has a frost later
  • Typical last frostMay 850% chance of a frost after it
  • Typical first fall frostOctober 250% chance of a frost before it
  • Frost-free season147 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Onida, SDSpring: a frost after April 25 in 9 years out of 10, after May 8 in half of the years, after May 22 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 15 in 9 years out of 10. Typical frost-free season: 147 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 8First frost ~Oct 2Frost season at Onida, SDSpring: a frost after April 25 in 9 years out of 10, after May 8 in half of the years, after May 22 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 15 in 9 years out of 10. Typical frost-free season: 147 days.JFMAMJJASONDLast frost ~May 8First 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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 22September 19
50% (typical)May 8October 2
90% (likely)April 25October 15
Frost-free season (32°F, 50% chance)
147 days
Hard frost (28°F), last in spring, 50% chance after
April 29
Hard frost (28°F), first in fall, 50% chance before
October 11

The last 15 years (2006–2020 normals)

Typical last frost May 9 (1 day later than the 30-year normal), typical first fall frost October 3 (1 day later). Frost-free season 146 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 Onida: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 22, 20% May 17, 30% May 14, 40% May 10, 50% May 8, 60% May 5, 70% May 3, 80% April 30, 90% April 25. Observed last spring frost in recent years: 2021 May 12, 2022 May 21, 2023 May 2, 2024 May 3, 2025 April 29, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 22May 8Apr 252021: May 122022: May 212023: May 22024: May 32025: April 292026: May 7Fall at Onida: 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 29, 50% October 2, 60% October 5, 70% October 7, 80% October 11, 90% October 15. Observed first fall frost in recent years: 2021 October 21, 2022 October 7, 2023 October 9, 2024 October 14, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 19Oct 2Oct 152021: October 212022: October 72023: October 92024: October 142025: 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 12October 21
2022May 21October 7
2023May 2October 9
2024May 3October 14
2025April 29October 13
2026May 7season not over yet

What these dates mean

May 22 is the cautious spring light-frost date for Onida; with only a 10 % chance of a light frost later, it marks the point when a gardener can reliably set out tender crops.

The median light-frost dates are May 8 in spring and October 2 in fall; each carries a 50 % chance of a light frost occurring after or before them respectively. The median hard-frost dates are April 29 for spring and October 11 for fall, providing the even-odds reference for more severe freezes. In the autumn, September 19 serves as the cautious fall light-frost date, offering a 10 % chance that a light frost has arrived earlier and thus an appropriate moment to finish harvesting tender crops.

A hard frost at 28 °F can damage plants that survive a 32 °F light frost, so the hard-frost dates are critical for understanding the deeper risk.

How to read the probabilities

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

  • Spring: "10% after May 22" 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 Onida, SDNumbered nearest stations: 1 — Pierre, SD — 25 mi; 2 — Highmore, SD — 37 mi; 3 — Faulkton, SD — 54 mi; 4 — Selby, SD — 54 mi; 5 — Kennebec, SD — 59 mi.SD50 mi · 80 km1. Pierre, SD — 25 mi12. Highmore, SD — 37 mi23. Faulkton, SD — 54 mi34. Selby, SD — 54 mi45. Kennebec, SD — 59 mi5
  1. Pierre, SD 25 mi (41 km)
  2. Highmore, SD 37 mi (59 km)
  3. Faulkton, SD 54 mi (86 km)
  4. Selby, SD 54 mi (87 km)
  5. Kennebec, SD 59 mi (95 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: 44.7322, -100.1447.