U.S. Frost Dates by Weather Station

NOAA station USC00191386 · Massachusetts

Frost Dates for Chatham, MA

NOAA weather station Chatham (USC00191386), Massachusetts · elevation 40 ft (12 m) · hardiness zone 7b*

  • Lower-risk planting dateafter April 18only 1 spring in 10 still has a frost later
  • Typical last frostApril 550% chance of a frost after it
  • Typical first fall frostNovember 1550% chance of a frost before it
  • Frost-free season221 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season at Chatham, MASpring: a frost after March 27 in 9 years out of 10, after April 5 in half of the years, after April 18 in 1 year out of 10. Fall: the first frost comes before November 1 in 1 year out of 10, before November 15 in half of the years, before November 30 in 9 years out of 10. Typical frost-free season: 221 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 5First frost ~Nov 15Frost season at Chatham, MASpring: a frost after March 27 in 9 years out of 10, after April 5 in half of the years, after April 18 in 1 year out of 10. Fall: the first frost comes before November 1 in 1 year out of 10, before November 15 in half of the years, before November 30 in 9 years out of 10. Typical frost-free season: 221 days.JFMAMJJASONDLast frost ~Apr 5First frost ~Nov 15
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 18November 1
50% (typical)April 5November 15
90% (likely)March 27November 30
Frost-free season (32°F, 50% chance)
221 days
Hard frost (28°F), last in spring, 50% chance after
March 28
Hard frost (28°F), first in fall, 50% chance before
November 26

The last 15 years (2006–2020 normals)

Typical last frost April 5 (same as the 30-year normal), typical first fall frost November 16 (1 day later). Frost-free season 224 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 Chatham: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 18, 20% April 12, 30% April 10, 40% April 7, 50% April 5, 60% April 3, 70% April 2, 80% March 31, 90% March 27.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 18Apr 5Mar 27Fall at Chatham: chance of a frost before this dateFall, chance of a frost before the date: 10% November 1, 20% November 5, 30% November 9, 40% November 12, 50% November 15, 60% November 17, 70% November 20, 80% November 24, 90% November 30.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Nov 1Nov 15Nov 30
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

April 18 is the cautious spring date that lets a gardener plan to set out tender crops, with only a 10 % chance of a light frost occurring later. The 50 % spring date is April 5, meaning there is an even chance of a light frost later than this date, while the 90 % date of March 27 indicates a gamble for early planting.

For the autumn season the cautious date is November 1, when a light frost has only a 10 % chance of arriving earlier, allowing growers to finish harvesting tender crops. The 50 % fall date is November 15, giving a 50 % chance of a light frost earlier than this date, and the 90 % date of November 30 marks a gamble for later crops.

Hard frost, recorded at 28 °F, is more damaging than light frost at 32 °F; its 50 % dates are March 28 in spring and November 26 in fall, highlighting when the risk of the colder, more harmful freeze is balanced.

How to read the probabilities

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

  • Spring: "10% after April 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 November 1" 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 Chatham, MANumbered nearest stations: 1 — Hyannis, MA — 18 mi; 2 — Edgartown, MA — 34 mi; 3 — Rochester, MA — 50 mi; 4 — Hingham, MA — 63 mi; 5 — Blue Hill Coop, MA — 71 mi.RICT25 mi · 40 km1. Hyannis, MA — 18 mi12. Edgartown, MA — 34 mi23. Rochester, MA — 50 mi34. Hingham, MA — 63 mi45. Blue Hill Coop, MA — 71 mi5
  1. Hyannis, MA 18 mi (29 km)
  2. Edgartown, MA 34 mi (55 km)
  3. Rochester, MA 50 mi (81 km)
  4. Hingham, MA 63 mi (101 km)
  5. Blue Hill Coop, MA 71 mi (114 km)

Sources

* Hardiness zone 7b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 41.6569, -69.9592.