U.S. Frost Dates by Weather Station

NOAA station USC00397073 · South Dakota

Frost Dates for Red Owl, SD

NOAA weather station Red Owl (USC00397073), South Dakota · elevation 2773 ft (845 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 27only 1 spring in 10 still has a frost later
  • Typical last frostMay 1650% chance of a frost after it
  • Typical first fall frostSeptember 2650% chance of a frost before it
  • Frost-free season131 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Red Owl, SDSpring: a frost after May 4 in 9 years out of 10, after May 16 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 11 in 1 year out of 10, before September 26 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 131 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 16First frost ~Sep 26Frost season at Red Owl, SDSpring: a frost after May 4 in 9 years out of 10, after May 16 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 11 in 1 year out of 10, before September 26 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 131 days.JFMAMJJASONDLast frost ~May 16First 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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 27September 11
50% (typical)May 16September 26
90% (likely)May 4October 8
Frost-free season (32°F, 50% chance)
131 days
Hard frost (28°F), last in spring, 50% chance after
May 6
Hard frost (28°F), first in fall, 50% chance before
October 3

The last 15 years (2006–2020 normals)

Typical last frost May 14 (2 days earlier than the 30-year normal), typical first fall frost September 28 (2 days later). Frost-free season 136 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 Red Owl: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 27, 20% May 24, 30% May 21, 40% May 18, 50% May 16, 60% May 13, 70% May 11, 80% May 8, 90% May 4.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 27May 16May 4Fall at Red Owl: chance of a frost before this dateFall, chance of a frost before the date: 10% September 11, 20% September 17, 30% September 20, 40% September 23, 50% September 26, 60% September 29, 70% October 1, 80% October 4, 90% October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 11Sep 26Oct 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.

What these dates mean

The 131 days between the 32°F 50% dates in Red Owl span the interval when a light frost is less likely to interrupt garden work. The 50% date in spring is May 16, meaning there is a 50% chance of a light frost later than that day. In fall the 50% date is September 26, meaning there is a 50% chance of a light frost earlier than that day. The hard-frost 50% dates are May 6 and October 3.

For a cautious spring planting schedule, the date with only a 10% chance of a light frost later is May 27, while the cautious date to finish tender-crop harvesting in fall is September 11, each offering the lowest risk among the three spring and three fall dates. A hard frost at 28°F can damage or kill plants that might survive a light frost at 32°F, making those hard-frost dates a more critical threshold for garden planning.

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 11" 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 Red Owl, SDNumbered nearest stations: 1 — Maurine, SD — 12 mi; 2 — Elm Springs, SD — 27 mi; 3 — Newell, SD — 42 mi; 4 — Milesville, SD — 48 mi; 5 — near Sturgis, SD — 49 mi.SD25 mi · 40 km1. Maurine, SD — 12 mi12. Elm Springs, SD — 27 mi23. Newell, SD — 42 mi34. Milesville, SD — 48 mi45. near Sturgis, SD — 49 mi5
  1. Maurine, SD 12 mi (19 km)
  2. Elm Springs, SD 27 mi (43 km)
  3. Newell, SD 42 mi (68 km)
  4. Milesville, SD 48 mi (77 km)
  5. near Sturgis, SD 49 mi (79 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: 44.6981, -102.5608.