U.S. Frost Dates by Weather Station

NOAA station USC00190736 · Massachusetts

Frost Dates for Blue Hill Coop, MA

NOAA weather station Blue Hill Coop (USC00190736), Massachusetts · elevation 625 ft (191 m) · hardiness zone 6b*

  • Lower-risk planting dateafter April 30only 1 spring in 10 still has a frost later
  • Typical last frostApril 1850% chance of a frost after it
  • Typical first fall frostOctober 2650% chance of a frost before it
  • Frost-free season190 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Blue Hill Coop, MASpring: a frost after April 7 in 9 years out of 10, after April 18 in half of the years, after April 30 in 1 year out of 10. Fall: the first frost comes before October 9 in 1 year out of 10, before October 26 in half of the years, before November 8 in 9 years out of 10. Typical frost-free season: 190 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 18First frost ~Oct 26Frost season at Blue Hill Coop, MASpring: a frost after April 7 in 9 years out of 10, after April 18 in half of the years, after April 30 in 1 year out of 10. Fall: the first frost comes before October 9 in 1 year out of 10, before October 26 in half of the years, before November 8 in 9 years out of 10. Typical frost-free season: 190 days.JFMAMJJASONDLast frost ~Apr 18First frost ~Oct 26
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 30October 9
50% (typical)April 18October 26
90% (likely)April 7November 8
Frost-free season (32°F, 50% chance)
190 days
Hard frost (28°F), last in spring, 50% chance after
April 6
Hard frost (28°F), first in fall, 50% chance before
November 5

The last 15 years (2006–2020 normals)

Typical last frost April 17 (1 day earlier than the 30-year normal), typical first fall frost October 28 (2 days later). Frost-free season 194 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 Blue Hill Coop: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 30, 20% April 25, 30% April 22, 40% April 20, 50% April 18, 60% April 16, 70% April 13, 80% April 10, 90% April 7. Observed last spring frost in recent years: 2021 April 23, 2022 April 18, 2023 April 8, 2024 April 26, 2025 April 11, 2026 April 21.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 30Apr 18Apr 72021: April 232022: April 182023: April 82024: April 262025: April 112026: April 21Fall at Blue Hill Coop: chance of a frost before this dateFall, chance of a frost before the date: 10% October 9, 20% October 15, 30% October 19, 40% October 22, 50% October 26, 60% October 29, 70% November 1, 80% November 3, 90% November 8. Observed first fall frost in recent years: 2021 November 4, 2022 November 9, 2023 November 2, 2024 November 3, 2025 November 7.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 9Oct 26Nov 82021: November 42022: November 92023: November 22024: November 32025: November 7
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
2021April 23November 4
2022April 18November 9
2023April 8November 2
2024April 26November 3
2025April 11November 7
2026April 21season not over yet

What these dates mean

April 30 is the cautious spring date at Blue Hill Coop, allowing a gardener to set out tender crops with only a 10% chance of a later light frost. The 50% date in spring is April 18; at that point there is a 50% chance of a light frost later, so it marks a median risk threshold. October 9 is the cautious fall date, giving a gardener a 10% chance that a light frost has already arrived and signalling when to finish harvesting tender crops. The 50% date in fall is October 26, indicating a 50% chance of a light frost earlier. The hard-frost 50% dates are April 6 in spring and November 5 in fall; these dates identify when a 28 °F frost is equally likely to have occurred or not. A hard frost at 28 °F can injure or kill plants that survive a light frost at 32 °F, making it a more critical concern.

How to read the probabilities

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

  • Spring: "10% after April 30" 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 9" 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 Blue Hill Coop, MANumbered nearest stations: 1 — Jamaica Plain, MA — 6 mi; 2 — Hingham, MA — 10 mi; 3 — near Boston, MA — 12 mi; 4 — Reading, MA — 22 mi; 5 — Marblehead, MA — 24 mi.MANHCTRIVT25 mi · 40 km1. Jamaica Plain, MA — 6 mi12. Hingham, MA — 10 mi23. near Boston, MA — 12 mi34. Reading, MA — 22 mi45. Marblehead, MA — 24 mi5
  1. Jamaica Plain, MA 6 mi (10 km)
  2. Hingham, MA 10 mi (17 km)
  3. near Boston, MA 12 mi (19 km)
  4. Reading, MA 22 mi (35 km)
  5. Marblehead, MA 24 mi (38 km)

Sources

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

Station coordinates: 42.2122, -71.1136.