U.S. Frost Dates by Weather Station

NOAA station USC00120830 · Indiana

Frost Dates for Bluffton, IN

NOAA weather station Bluffton 6 N (USC00120830), Indiana · elevation 861 ft (262 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 9only 1 spring in 10 still has a frost later
  • Typical last frostApril 2450% chance of a frost after it
  • Typical first fall frostOctober 2050% chance of a frost before it
  • Frost-free season179 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Bluffton, INSpring: a frost after April 10 in 9 years out of 10, after April 24 in half of the years, after May 9 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 20 in half of the years, before November 3 in 9 years out of 10. Typical frost-free season: 179 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 24First frost ~Oct 20Frost season at Bluffton, INSpring: a frost after April 10 in 9 years out of 10, after April 24 in half of the years, after May 9 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 20 in half of the years, before November 3 in 9 years out of 10. Typical frost-free season: 179 days.JFMAMJJASONDLast frost ~Apr 24First frost ~Oct 20
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 9October 6
50% (typical)April 24October 20
90% (likely)April 10November 3
Frost-free season (32°F, 50% chance)
179 days
Hard frost (28°F), last in spring, 50% chance after
April 12
Hard frost (28°F), first in fall, 50% chance before
November 1

The last 15 years (2006–2020 normals)

Typical last frost April 24 (same as the 30-year normal), typical first fall frost October 22 (2 days later). Frost-free season 180 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 Bluffton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 9, 20% May 3, 30% April 30, 40% April 27, 50% April 24, 60% April 21, 70% April 18, 80% April 16, 90% April 10.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 9Apr 24Apr 10Fall at Bluffton: chance of a frost before this dateFall, chance of a frost before the date: 10% October 6, 20% October 11, 30% October 15, 40% October 17, 50% October 20, 60% October 23, 70% October 26, 80% October 30, 90% November 3.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 6Oct 20Nov 3
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.

What these dates mean

Planting tender crops on the early spring date of April 10 is a gamble, because there is a 90 % chance of a frost later in the season.

The 50 % spring date, April 24, marks the point where the probability of a frost later is equal, while the 50 % fall date, October 20, marks equal odds of a frost earlier. For a low-risk plan, Bluffton gardeners use the cautious spring date of May 9, which carries only a 10 % chance of a frost later, and the cautious fall date of October 6, which carries only a 10 % chance of a frost earlier. These probabilities are derived from a 27-year record.

Hard frost, reaching 28 °F on its 50 % dates of April 12 and November 1, can damage plant tissue that survives the lighter 32 °F frost.

How to read the probabilities

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

  • Spring: "10% after May 9" 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 October 6" 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 Bluffton, INNumbered nearest stations: 1 — Fort Wayne, IN — 11 mi; 2 — Berne, IN — 15 mi; 3 — Huntington, IN — 18 mi; 4 — Hartford City, IN — 27 mi; 5 — Columbia City, IN — 29 mi.INOH25 mi · 40 km1. Fort Wayne, IN — 11 mi12. Berne, IN — 15 mi23. Huntington, IN — 18 mi34. Hartford City, IN — 27 mi45. Columbia City, IN — 29 mi5
  1. Fort Wayne, IN 11 mi (18 km)
  2. Berne, IN 15 mi (25 km)
  3. Huntington, IN 18 mi (29 km)
  4. Hartford City, IN 27 mi (44 km)
  5. Columbia City, IN 29 mi (46 km)

Sources

* Hardiness zone 6a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 40.8142, -85.1547.