U.S. Frost Dates by Weather Station

NOAA station USC00194744 · Massachusetts

Frost Dates for Middleton, MA

NOAA weather station Middleton (USC00194744), Massachusetts · elevation 110 ft (34 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 20only 1 spring in 10 still has a frost later
  • Typical last frostMay 350% chance of a frost after it
  • Typical first fall frostOctober 950% chance of a frost before it
  • Frost-free season157 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Middleton, MASpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 29 in 1 year out of 10, before October 9 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 157 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 3First frost ~Oct 9Frost season at Middleton, MASpring: a frost after April 20 in 9 years out of 10, after May 3 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 29 in 1 year out of 10, before October 9 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 157 days.JFMAMJJASONDLast frost ~May 3First frost ~Oct 9
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)May 20September 29
50% (typical)May 3October 9
90% (likely)April 20October 24
Frost-free season (32°F, 50% chance)
157 days
Hard frost (28°F), last in spring, 50% chance after
April 21
Hard frost (28°F), first in fall, 50% chance before
October 21

The last 15 years (2006–2020 normals)

Typical last frost April 28 (5 days earlier than the 30-year normal), typical first fall frost October 15 (6 days later). Frost-free season 169 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 Middleton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 20, 20% May 14, 30% May 9, 40% May 6, 50% May 3, 60% May 1, 70% April 28, 80% April 25, 90% April 20. Observed last spring frost in recent years: 2021 April 23, 2022 May 1, 2023 May 18, 2024 April 27, 2025 April 21, 2026 April 26.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 20May 3Apr 202021: April 232022: May 12023: May 182024: April 272025: April 212026: April 26Fall at Middleton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 29, 20% October 2, 30% October 4, 40% October 7, 50% October 9, 60% October 12, 70% October 15, 80% October 18, 90% October 24. Observed first fall frost in recent years: 2021 November 2, 2022 October 29, 2023 November 1, 2024 October 13, 2025 October 10.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 29Oct 9Oct 242021: November 22022: October 292023: November 12024: October 132025: October 10
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 2
2022May 1October 29
2023May 18November 1
2024April 27October 13
2025April 21October 10
2026April 26season not over yet

What these dates mean

The 157 days between the two 32 °F 50% dates in Middleton, Massachusetts, define the core growing window where light-frost risk is balanced. The 50% date is May 3 for spring and the 50% date is October 9 for fall; at each of those points a light frost is equally likely to have occurred or not. The hard-frost 50% dates are April 21 in spring and October 21 in fall, marking when a 28 °F frost is as likely as not.

For a cautious plan, gardeners should wait until the May 20 date, which carries only a 10 % chance of a light frost later, before setting out tender crops. In the autumn, the September 29 date is the cautious point, offering just a 10 % chance that a light frost has arrived earlier, making it the safe time to finish harvesting tender crops.

A hard frost at 28 °F can damage or kill plants that survive a light frost at 32 °F, so the hard-frost dates represent a stricter limit on plant viability.

How to read the probabilities

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

  • Spring: "10% after May 20" 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 29" 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 Middleton, MANumbered nearest stations: 1 — Reading, MA — 7 mi; 2 — Marblehead, MA — 10 mi; 3 — Lawrence, MA — 10 mi; 4 — Groveland, MA — 11 mi; 5 — Haverhill, MA — 12 mi.MANHVTME25 mi · 40 km1. Reading, MA — 7 mi12. Marblehead, MA — 10 mi23. Lawrence, MA — 10 mi34. Groveland, MA — 11 mi45. Haverhill, MA — 12 mi5
  1. Reading, MA 7 mi (12 km)
  2. Marblehead, MA 10 mi (16 km)
  3. Lawrence, MA 10 mi (17 km)
  4. Groveland, MA 11 mi (17 km)
  5. Haverhill, MA 12 mi (19 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: 42.5933, -71.0186.