U.S. Frost Dates by Weather Station

NOAA station USC00190120 · Massachusetts

Frost Dates for Amherst, MA

NOAA weather station Amherst (USC00190120), Massachusetts · elevation 145 ft (44 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 19only 1 spring in 10 still has a frost later
  • Typical last frostMay 550% chance of a frost after it
  • Typical first fall frostOctober 850% chance of a frost before it
  • Frost-free season156 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Amherst, MASpring: a frost after April 23 in 9 years out of 10, after May 5 in half of the years, after May 19 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 8 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 156 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 5First frost ~Oct 8Frost season at Amherst, MASpring: a frost after April 23 in 9 years out of 10, after May 5 in half of the years, after May 19 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 8 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 156 days.JFMAMJJASONDLast frost ~May 5First frost ~Oct 8
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 19September 28
50% (typical)May 5October 8
90% (likely)April 23October 23
Frost-free season (32°F, 50% chance)
156 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
October 21

The last 15 years (2006–2020 normals)

Typical last frost May 1 (4 days earlier than the 30-year normal), typical first fall frost October 14 (6 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 Amherst: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 19, 20% May 15, 30% May 11, 40% May 7, 50% May 5, 60% May 2, 70% April 30, 80% April 26, 90% April 23. Observed last spring frost in recent years: 2021 April 27, 2022 May 1, 2023 May 18, 2024 April 26, 2025 April 21, 2026 April 25.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 19May 5Apr 232021: April 272022: May 12023: May 182024: April 262025: April 212026: April 25Fall at Amherst: chance of a frost before this dateFall, chance of a frost before the date: 10% September 28, 20% October 1, 30% October 3, 40% October 5, 50% October 8, 60% October 11, 70% October 14, 80% October 18, 90% October 23. Observed first fall frost in recent years: 2021 October 24, 2022 October 9, 2023 October 31, 2024 October 13, 2025 October 10.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 28Oct 8Oct 232021: October 242022: October 92023: October 312024: 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 27October 24
2022May 1October 9
2023May 18October 31
2024April 26October 13
2025April 21October 10
2026April 25season not over yet

What these dates mean

The 156 days between the 50% dates in Amherst, May 5 and October 8, define the interval when the average temperature stays above the light-frost threshold, giving a window for tender crops. For a gardener, the 50% dates are reference points: a 50% chance of a light frost later than May 5 in spring and a 50% chance of a light frost earlier than October 8 in fall. A cautious plan would wait until May 19, which carries only a 10% chance of a later frost, before setting out tender crops, and would aim to finish harvesting by September 28, when only a 10% chance of an earlier frost exists.

Planting as early as April 23 or as late as October 23 raises the risk to 90% and is considered a gamble. The hard-frost 50% dates are April 23 and October 21, and a hard frost at 28°F can damage or kill plants that would survive a light frost at 32°F, so it matters more.

How to read the probabilities

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

  • Spring: "10% after May 19" 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 28" 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 Amherst, MANumbered nearest stations: 1 — Worthington, MA — 20 mi; 2 — near Fiskdale, MA — 28 mi; 3 — Hartford (Bradley Airport), CT — 32 mi; 4 — Worcester, MA — 35 mi; 5 — Keene, NH — 40 mi.NYNHVTRI25 mi · 40 km1. Worthington, MA — 20 mi12. near Fiskdale, MA — 28 mi23. Hartford (Bradley Airport), CT — 32 mi34. Worcester, MA — 35 mi45. Keene, NH — 40 mi5
  1. Worthington, MA 20 mi (32 km)
  2. near Fiskdale, MA 28 mi (46 km)
  3. Hartford (Bradley Airport), CT 32 mi (51 km)
  4. Worcester, MA 35 mi (56 km)
  5. Keene, NH 40 mi (64 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: 42.3861, -72.5375.