U.S. Frost Dates by Weather Station

NOAA station USC00395090 · South Dakota

Frost Dates for Madison, SD

NOAA weather station Madison 2 SE (USC00395090), South Dakota · elevation 1643 ft (501 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 18only 1 spring in 10 still has a frost later
  • Typical last frostMay 550% chance of a frost after it
  • Typical first fall frostSeptember 3050% chance of a frost before it
  • Frost-free season148 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Madison, SDSpring: a frost after April 22 in 9 years out of 10, after May 5 in half of the years, after May 18 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before September 30 in half of the years, before October 13 in 9 years out of 10. Typical frost-free season: 148 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 5First frost ~Sep 30Frost season at Madison, SDSpring: a frost after April 22 in 9 years out of 10, after May 5 in half of the years, after May 18 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before September 30 in half of the years, before October 13 in 9 years out of 10. Typical frost-free season: 148 days.JFMAMJJASONDLast frost ~May 5First frost ~Sep 30
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.Today

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 18September 18
50% (typical)May 5September 30
90% (likely)April 22October 13
Frost-free season (32°F, 50% chance)
148 days
Hard frost (28°F), last in spring, 50% chance after
April 27
Hard frost (28°F), first in fall, 50% chance before
October 10

The last 15 years (2006–2020 normals)

Typical last frost May 6 (1 day later than the 30-year normal), typical first fall frost October 3 (3 days later). Frost-free season 149 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 Madison: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 18, 20% May 14, 30% May 11, 40% May 7, 50% May 5, 60% May 2, 70% April 30, 80% April 27, 90% April 22. Observed last spring frost in recent years: 2021 May 11, 2022 May 4, 2023 May 3, 2024 April 24, 2025 April 29, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 18May 5Apr 222021: May 112022: May 42023: May 32024: April 242025: April 292026: May 20Fall at Madison: chance of a frost before this dateFall, chance of a frost before the date: 10% September 18, 20% September 22, 30% September 26, 40% September 28, 50% September 30, 60% October 3, 70% October 5, 80% October 9, 90% October 13. Observed first fall frost in recent years: 2021 October 16, 2022 October 7, 2023 October 7, 2024 October 4, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 18Sep 30Oct 132021: October 162022: October 72023: October 72024: October 42025: October 22
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 11October 16
2022May 4October 7
2023May 3October 7
2024April 24October 4
2025April 29October 22
2026May 20season not over yet

What these dates mean

May 18 is the cautious spring date in Madison, carrying only a ten percent chance that a light frost (32 °F) will occur later, so gardeners can plan to set out tender crops after that day. The median, or 50% date, is May 5; at that point there is an even chance of a light frost occurring later in the season. The hard-frost 50% date of April 27 marks the point at which a 28 °F frost is equally likely to have happened or not.

In the autumn, September 18 serves as the cautious fall date, with only a ten percent chance that a light frost has already arrived, allowing growers to finish harvesting tender crops before frost risk rises. The 50% fall date is September 30, meaning the odds of a light frost earlier than that day are fifty-fifty. A hard frost at 28 °F is more damaging than a light frost at 32 °F because it can kill tissue that survives milder freezing.

How to read the probabilities

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

  • Spring: "10% after May 18" 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 18" 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 Madison, SDNumbered nearest stations: 1 — Flandreau, SD — 25 mi; 2 — Brookings, SD — 28 mi; 3 — Sioux Falls, SD — 33 mi; 4 — De Smet, SD — 35 mi; 5 — Bridgewater, SD — 37 mi.SDMNIA25 mi · 40 km1. Flandreau, SD — 25 mi12. Brookings, SD — 28 mi23. Sioux Falls, SD — 33 mi34. De Smet, SD — 35 mi45. Bridgewater, SD — 37 mi5
  1. Flandreau, SD 25 mi (41 km)
  2. Brookings, SD 28 mi (45 km)
  3. Sioux Falls, SD 33 mi (53 km)
  4. De Smet, SD 35 mi (57 km)
  5. Bridgewater, SD 37 mi (59 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: 43.9906, -97.0922.