U.S. Frost Dates by Weather Station

NOAA station USC00272174 · New Hampshire

Frost Dates for Durham, NH

NOAA weather station Durham (USC00272174), New Hampshire · elevation 75 ft (23 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 22only 1 spring in 10 still has a frost later
  • Typical last frostMay 850% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season148 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Durham, NHSpring: a frost after April 27 in 9 years out of 10, after May 8 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 23 in 1 year out of 10, before October 4 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 148 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 8First frost ~Oct 4Frost season at Durham, NHSpring: a frost after April 27 in 9 years out of 10, after May 8 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 23 in 1 year out of 10, before October 4 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 148 days.JFMAMJJASONDLast frost ~May 8First frost ~Oct 4
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 22September 23
50% (typical)May 8October 4
90% (likely)April 27October 20
Frost-free season (32°F, 50% chance)
148 days
Hard frost (28°F), last in spring, 50% chance after
April 27
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 5 (3 days earlier than the 30-year normal), typical first fall frost October 7 (3 days later). Frost-free season 154 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 Durham: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 22, 20% May 18, 30% May 14, 40% May 11, 50% May 8, 60% May 6, 70% May 3, 80% April 30, 90% April 27. Observed last spring frost in recent years: 2021 April 24, 2022 May 9, 2023 May 18, 2024 April 27.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 22May 8Apr 272021: April 242022: May 92023: May 182024: April 27Fall at Durham: chance of a frost before this dateFall, chance of a frost before the date: 10% September 23, 20% September 28, 30% October 1, 40% October 2, 50% October 4, 60% October 7, 70% October 10, 80% October 14, 90% October 20. Observed first fall frost in recent years: 2021 October 24, 2022 October 9, 2023 October 31, 2024 October 16.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 23Oct 4Oct 202021: October 242022: October 92023: October 312024: October 16
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 24October 24
2022May 9October 9
2023May 18October 31
2024April 27October 16
2025no dataincomplete record
2026incomplete recordseason not over yet

What these dates mean

The cautious fall date for finishing the harvest in Durham is September 23, when there is only a 10% chance a light frost has already arrived. In spring the cautious date for setting out tender crops is May 22, which carries a 10% chance of a frost later than that day, while planting on April 27 would be a gamble with a 90% chance of a frost later. The 50% date is May 8, and there is a 50% chance of a frost later than this date; the 50% fall date is October 4, with a 50% chance of a frost earlier than that date. Hard-frost median dates are April 27 in spring and October 15 in fall. A hard frost at 28 °F can damage or kill plants that survive a light frost at 32 °F, making it a more critical threshold for tender crops.

How to read the probabilities

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

  • Spring: "10% after May 22" 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 23" 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 Durham, NHNumbered nearest stations: 1 — Epping, NH — 10 mi; 2 — Greenland, NH — 11 mi; 3 — near Manchester, NH — 25 mi; 4 — Haverhill, MA — 27 mi; 5 — Groveland, MA — 28 mi.NHMAMEVT25 mi · 40 km1. Epping, NH — 10 mi12. Greenland, NH — 11 mi23. near Manchester, NH — 25 mi34. Haverhill, MA — 27 mi45. Groveland, MA — 28 mi5
  1. Epping, NH 10 mi (17 km)
  2. Greenland, NH 11 mi (17 km)
  3. near Manchester, NH 25 mi (40 km)
  4. Haverhill, MA 27 mi (44 km)
  5. Groveland, MA 28 mi (45 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: 43.1433, -70.95.