U.S. Frost Dates by Weather Station

NOAA station USC00391032 · South Dakota

Frost Dates for Bridgewater, SD

NOAA weather station Bridgewater (USC00391032), South Dakota · elevation 1417 ft (432 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 11only 1 spring in 10 still has a frost later
  • Typical last frostApril 3050% chance of a frost after it
  • Typical first fall frostOctober 750% chance of a frost before it
  • Frost-free season161 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Bridgewater, SDSpring: a frost after April 15 in 9 years out of 10, after April 30 in half of the years, after May 11 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: 161 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 30First frost ~Oct 7Frost season at Bridgewater, SDSpring: a frost after April 15 in 9 years out of 10, after April 30 in half of the years, after May 11 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: 161 days.JFMAMJJASONDLast frost ~Apr 30First 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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 11September 25
50% (typical)April 30October 7
90% (likely)April 15October 21
Frost-free season (32°F, 50% chance)
161 days
Hard frost (28°F), last in spring, 50% chance after
April 19
Hard frost (28°F), first in fall, 50% chance before
October 19

The last 15 years (2006–2020 normals)

Typical last frost April 30 (same as the 30-year normal), typical first fall frost October 11 (4 days later). Frost-free season 162 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 Bridgewater: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 11, 20% May 6, 30% May 3, 40% May 1, 50% April 30, 60% April 26, 70% April 23, 80% April 20, 90% April 15. Observed last spring frost in recent years: 2021 May 11, 2022 May 2, 2023 May 3, 2024 April 24, 2025 April 21, 2026 May 6.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 11Apr 30Apr 152021: May 112022: May 22023: May 32024: April 242025: April 212026: May 6Fall at Bridgewater: chance of a frost before this dateFall, chance of a frost before the date: 10% September 25, 20% September 30, 30% October 1, 40% October 4, 50% October 7, 60% October 10, 70% October 13, 80% October 16, 90% October 21. Observed first fall frost in recent years: 2021 October 16, 2022 October 7, 2023 October 7, 2024 October 14, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 25Oct 7Oct 212021: October 162022: October 72023: October 72024: October 142025: 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 2October 7
2023May 3October 7
2024April 24October 14
2025April 21October 22
2026May 6season not over yet

What these dates mean

The 161 days between the 50% dates in Bridgewater define the central window of light-frost risk. The median spring light-frost date is April 30 and the median fall light-frost date is October 7; these dates mark even odds of a frost occurring but are not themselves frost dates.

For a cautious planting plan, the spring date with only a 10 % chance of a later frost is May 11, while the fall date with only a 10 % chance of an earlier frost is September 25. Both dates give the lowest risk for setting out or finishing tender crops. A hard frost at 28 °F can injure plants that survive a light frost at 32 °F, so the median hard-frost dates—April 19 in spring and October 19 in fall—are important separate thresholds.

How to read the probabilities

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

  • Spring: "10% after May 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 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 Bridgewater, SDNumbered nearest stations: 1 — Alexandria, SD — 16 mi; 2 — Menno, SD — 22 mi; 3 — Madison, SD — 37 mi; 4 — Sioux Falls, SD — 39 mi; 5 — Tyndall, SD — 43 mi.IAMN25 mi · 40 km1. Alexandria, SD — 16 mi12. Menno, SD — 22 mi23. Madison, SD — 37 mi34. Sioux Falls, SD — 39 mi45. Tyndall, SD — 43 mi5
  1. Alexandria, SD 16 mi (26 km)
  2. Menno, SD 22 mi (36 km)
  3. Madison, SD 37 mi (59 km)
  4. Sioux Falls, SD 39 mi (62 km)
  5. Tyndall, SD 43 mi (69 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: 43.5525, -97.5017.