U.S. Frost Dates by Weather Station

NOAA station USC00396427 · South Dakota

Frost Dates near Colonial Pine Hills, SD

NOAA weather station Pactola Dam (USC00396427), South Dakota · elevation 4720 ft (1439 m) · hardiness zone 5a*

Colonial Pine Hills is the nearest town to the station (9.1 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter June 11only 1 spring in 10 still has a frost later
  • Typical last frostMay 2850% chance of a frost after it
  • Typical first fall frostSeptember 1850% chance of a frost before it
  • Frost-free season112 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season near Colonial Pine Hills, SDSpring: a frost after May 16 in 9 years out of 10, after May 28 in half of the years, after June 11 in 1 year out of 10. Fall: the first frost comes before September 4 in 1 year out of 10, before September 18 in half of the years, before October 1 in 9 years out of 10. Typical frost-free season: 112 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 28First frost ~Sep 18Frost season near Colonial Pine Hills, SDSpring: a frost after May 16 in 9 years out of 10, after May 28 in half of the years, after June 11 in 1 year out of 10. Fall: the first frost comes before September 4 in 1 year out of 10, before September 18 in half of the years, before October 1 in 9 years out of 10. Typical frost-free season: 112 days.JFMAMJJASONDLast frost ~May 28First frost ~Sep 18
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)June 11September 4
50% (typical)May 28September 18
90% (likely)May 16October 1
Frost-free season (32°F, 50% chance)
112 days
Hard frost (28°F), last in spring, 50% chance after
May 15
Hard frost (28°F), first in fall, 50% chance before
September 29

The last 15 years (2006–2020 normals)

Typical last frost May 25 (3 days earlier than the 30-year normal), typical first fall frost September 21 (3 days later). Frost-free season 115 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 near Colonial Pine Hills: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 11, 20% June 5, 30% June 1, 40% May 30, 50% May 28, 60% May 25, 70% May 22, 80% May 20, 90% May 16. Observed last spring frost in recent years: 2021 May 28, 2022 June 1, 2023 May 8, 2024 June 20, 2025 May 23, 2026 June 16.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 11May 28May 162021: May 282022: June 12023: May 82024: June 202025: May 232026: June 16Fall near Colonial Pine Hills: chance of a frost before this dateFall, chance of a frost before the date: 10% September 4, 20% September 9, 30% September 12, 40% September 16, 50% September 18, 60% September 21, 70% September 24, 80% September 27, 90% October 1. Observed first fall frost in recent years: 2021 September 17, 2022 October 7, 2023 October 6, 2024 September 22, 2025 September 5.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 4Sep 18Oct 12021: September 172022: October 72023: October 62024: September 222025: September 5
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 28September 17
2022June 1October 7
2023May 8October 6
2024June 20September 22
2025May 23September 5
2026June 16season not over yet

What these dates mean

September 4 marks the cautious fall date for finishing the harvest of tender crops in the Colonial Pine Hills area, with only a 10 % chance that a light frost has arrived earlier.

The 50% spring date, May 28, indicates a 50 % chance of a light frost later than that day, while the 50% fall date, September 18, indicates a 50 % chance of a light frost earlier than that day. Gardeners who prefer minimal risk should plan to set out tender crops after the cautious spring date of June 11 and to complete harvesting before the cautious fall date of September 4. The record shows 112 days between the two 32°F 50% dates over 27 years.

Hard frosts at 28 °F, such as the median dates May 15 and September 29, can damage plants more severely than the milder 32 °F light frosts.

How to read the probabilities

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

  • Spring: "10% after June 11" 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 4" 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 Colonial Pine Hills, SDNumbered nearest stations: 1 — Hill City, SD — 10 mi; 2 — near Blackhawk, SD — 11 mi; 3 — Mount Rushmore National Memorial, SD — 13 mi; 4 — Custer, SD — 21 mi; 5 — Rapid City (Airport), SD — 21 mi.WY25 mi · 40 km1. Hill City, SD — 10 mi12. near Blackhawk, SD — 11 mi23. Mount Rushmore National Memorial, SD — 13 mi34. Custer, SD — 21 mi45. Rapid City (Airport), SD — 21 mi5
  1. Hill City, SD 10 mi (15 km)
  2. near Blackhawk, SD 11 mi (17 km)
  3. Mount Rushmore National Memorial, SD 13 mi (21 km)
  4. Custer, SD 21 mi (34 km)
  5. Rapid City (Airport), SD 21 mi (34 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: 44.0622, -103.4819.