U.S. Frost Dates by Weather Station

NOAA station USC00391294 · South Dakota

Frost Dates for Camp Crook, SD

NOAA weather station Camp Crook (USC00391294), South Dakota · elevation 3120 ft (951 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 30only 1 spring in 10 still has a frost later
  • Typical last frostMay 1750% chance of a frost after it
  • Typical first fall frostSeptember 2450% chance of a frost before it
  • Frost-free season128 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Camp Crook, SDSpring: a frost after May 4 in 9 years out of 10, after May 17 in half of the years, after May 30 in 1 year out of 10. Fall: the first frost comes before September 9 in 1 year out of 10, before September 24 in half of the years, before October 7 in 9 years out of 10. Typical frost-free season: 128 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 17First frost ~Sep 24Frost season at Camp Crook, SDSpring: a frost after May 4 in 9 years out of 10, after May 17 in half of the years, after May 30 in 1 year out of 10. Fall: the first frost comes before September 9 in 1 year out of 10, before September 24 in half of the years, before October 7 in 9 years out of 10. Typical frost-free season: 128 days.JFMAMJJASONDLast frost ~May 17First frost ~Sep 24
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 30September 9
50% (typical)May 17September 24
90% (likely)May 4October 7
Frost-free season (32°F, 50% chance)
128 days
Hard frost (28°F), last in spring, 50% chance after
May 4
Hard frost (28°F), first in fall, 50% chance before
October 3

The last 15 years (2006–2020 normals)

Typical last frost May 13 (4 days earlier than the 30-year normal), typical first fall frost September 28 (4 days later). Frost-free season 134 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 Camp Crook: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 30, 20% May 26, 30% May 22, 40% May 19, 50% May 17, 60% May 13, 70% May 10, 80% May 7, 90% May 4. Observed last spring frost in recent years: 2021 May 13, 2022 May 22, 2023 May 1, 2024 June 19, 2025 May 17, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 30May 17May 42021: May 132022: May 222023: May 12024: June 192025: May 172026: May 7Fall at Camp Crook: chance of a frost before this dateFall, chance of a frost before the date: 10% September 9, 20% September 14, 30% September 18, 40% September 21, 50% September 24, 60% September 27, 70% September 30, 80% October 3, 90% October 7. Observed first fall frost in recent years: 2021 October 12, 2022 October 7, 2023 October 6, 2024 September 22, 2025 September 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 9Sep 24Oct 72021: October 122022: October 72023: October 62024: September 222025: September 6
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 13October 12
2022May 22October 7
2023May 1October 6
2024June 19September 22
2025May 17September 6
2026May 7season not over yet

What these dates mean

The cautious spring date is May 30, when there is only a 10% chance of a light frost later, allowing a gardener to set out tender crops with minimal risk.

The 50% dates are May 17 for spring and September 24 for fall; each represents the moment when a light frost has a 50% probability, providing a neutral reference for timing decisions.

For the autumn schedule, the cautious date is September 9, when there is only a 10% chance that a light frost has already arrived, indicating the latest reliable time to finish harvesting tender crops. The hard-frost median dates are May 4 in spring and October 3 in fall, and a hard frost at 28 °F can damage plants that survive a light frost, making it a more critical threshold.

How to read the probabilities

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

  • Spring: "10% after May 30" 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 9" 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 Camp Crook, SDNumbered nearest stations: 1 — Ridgeway, MT — 23 mi; 2 — Ekalaka, MT — 36 mi; 3 — Bowman, ND — 53 mi; 4 — Powderville, MT — 55 mi; 5 — Belle Fourche, SD — 61 mi.MTSDWY50 mi · 80 km1. Ridgeway, MT — 23 mi12. Ekalaka, MT — 36 mi23. Bowman, ND — 53 mi34. Powderville, MT — 55 mi45. Belle Fourche, SD — 61 mi5
  1. Ridgeway, MT 23 mi (37 km)
  2. Ekalaka, MT 36 mi (58 km)
  3. Bowman, ND 53 mi (86 km)
  4. Powderville, MT 55 mi (89 km)
  5. Belle Fourche, SD 61 mi (98 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: 45.5489, -103.9744.