U.S. Frost Dates by Weather Station

NOAA station USC00391621 · South Dakota

Frost Dates for Chamberlain, SD

NOAA weather station Chamberlain 5 S (USC00391621), South Dakota · elevation 1704 ft (519 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 350% chance of a frost after it
  • Typical first fall frostOctober 750% chance of a frost before it
  • Frost-free season156 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Chamberlain, SDSpring: a frost after April 19 in 9 years out of 10, after May 3 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 7 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 156 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 3First frost ~Oct 7Frost season at Chamberlain, SDSpring: a frost after April 19 in 9 years out of 10, after May 3 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 7 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 156 days.JFMAMJJASONDLast frost ~May 3First frost ~Oct 7
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 17September 25
50% (typical)May 3October 7
90% (likely)April 19October 21
Frost-free season (32°F, 50% chance)
156 days
Hard frost (28°F), last in spring, 50% chance after
April 24
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost May 3 (same as the 30-year normal), typical first fall frost October 11 (4 days later). Frost-free season 159 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 Chamberlain: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 11, 30% May 8, 40% May 5, 50% May 3, 60% May 1, 70% April 29, 80% April 25, 90% April 19. Observed last spring frost in recent years: 2021 May 10, 2022 April 28, 2023 May 3, 2024 April 22, 2025 April 20, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 3Apr 192021: May 102022: April 282023: May 32024: April 222025: April 202026: May 7Fall at Chamberlain: chance of a frost before this dateFall, chance of a frost before the date: 10% September 25, 20% September 29, 30% October 1, 40% October 4, 50% October 7, 60% October 10, 70% October 13, 80% October 17, 90% October 21. Observed first fall frost in recent years: 2021 October 21, 2022 October 7, 2023 October 7, 2024 October 15, 2025 October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 25Oct 7Oct 212021: October 212022: October 72023: October 72024: October 152025: October 23
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 10October 21
2022April 28October 7
2023May 3October 7
2024April 22October 15
2025April 20October 23
2026May 7season not over yet

What these dates mean

The cautious fall date in Chamberlain for finishing the harvest is September 25, when there is only a 10% chance of a light frost earlier than that date. After that point the risk rises, and October 21 carries a 90% chance of a frost earlier, making late-season tender crops a gamble.

In spring the cautious date for setting out tender crops is May 17, with a 10% chance of a light frost later than that date; planting on April 19 would face a 90% chance and is a gamble. The 50% date is May 3, and there is a 50% chance of a light frost later than this date. The 50% hard-frost date in spring is April 24, with a 50% chance of a hard frost later than this date.

The 50% date is October 7, and there is a 50% chance of a light frost earlier than this date; the 50% hard-frost date in fall is October 17, with a 50% chance of a hard frost earlier than this date. A hard frost at 28 °F can damage plant tissue that typically survives a light frost at 32 °F.

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 25" 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 Chamberlain, SDNumbered nearest stations: 1 — Academy, SD — 21 mi; 2 — Kennebec, SD — 30 mi; 3 — White Lake, SD — 32 mi; 4 — Gregory, SD — 35 mi; 5 — Wessington Springs, SD — 44 mi.25 mi · 40 km1. Academy, SD — 21 mi12. Kennebec, SD — 30 mi23. White Lake, SD — 32 mi34. Gregory, SD — 35 mi45. Wessington Springs, SD — 44 mi5
  1. Academy, SD 21 mi (34 km)
  2. Kennebec, SD 30 mi (48 km)
  3. White Lake, SD 32 mi (52 km)
  4. Gregory, SD 35 mi (56 km)
  5. Wessington Springs, SD 44 mi (70 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: 43.7353, -99.3125.