U.S. Frost Dates by Weather Station

NOAA station USC00271647 · New Hampshire

Frost Dates for Colebrook, NH

NOAA weather station Colebrook 3 SW (USC00271647), New Hampshire · elevation 1120 ft (341 m) · hardiness zone 4a*

  • Lower-risk planting dateafter June 14only 1 spring in 10 still has a frost later
  • Typical last frostMay 3150% chance of a frost after it
  • Typical first fall frostSeptember 2150% chance of a frost before it
  • Frost-free season112 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Colebrook, NHSpring: a frost after May 16 in 9 years out of 10, after May 31 in half of the years, after June 14 in 1 year out of 10. Fall: the first frost comes before September 7 in 1 year out of 10, before September 21 in half of the years, before October 2 in 9 years out of 10. Typical frost-free season: 112 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 31First frost ~Sep 21Frost season at Colebrook, NHSpring: a frost after May 16 in 9 years out of 10, after May 31 in half of the years, after June 14 in 1 year out of 10. Fall: the first frost comes before September 7 in 1 year out of 10, before September 21 in half of the years, before October 2 in 9 years out of 10. Typical frost-free season: 112 days.JFMAMJJASONDLast frost ~May 31First frost ~Sep 21
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)June 14September 7
50% (typical)May 31September 21
90% (likely)May 16October 2
Frost-free season (32°F, 50% chance)
112 days
Hard frost (28°F), last in spring, 50% chance after
May 17
Hard frost (28°F), first in fall, 50% chance before
October 1

The last 15 years (2006–2020 normals)

Typical last frost May 27 (4 days earlier than the 30-year normal), typical first fall frost September 23 (2 days later). Frost-free season 118 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 Colebrook: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 14, 20% June 8, 30% June 4, 40% June 2, 50% May 31, 60% May 28, 70% May 25, 80% May 21, 90% May 16. Observed last spring frost in recent years: 2021 May 30, 2022 May 25, 2023 May 27, 2024 April 28, 2026 May 24.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 14May 31May 162021: May 302022: May 252023: May 272024: April 282026: May 24Fall at Colebrook: chance of a frost before this dateFall, chance of a frost before the date: 10% September 7, 20% September 11, 30% September 15, 40% September 18, 50% September 21, 60% September 23, 70% September 26, 80% September 29, 90% October 2. Observed first fall frost in recent years: 2021 October 24, 2022 September 30, 2023 October 24, 2024 October 13, 2025 September 20.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 7Sep 21Oct 22021: October 242022: September 302023: October 242024: October 132025: September 20
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
2021May 30October 24
2022May 25September 30
2023May 27October 24
2024April 28October 13
2025incomplete recordSeptember 20
2026May 24season not over yet

What these dates mean

June 14 is the cautious spring date, with only a 10 % chance of a light frost later, so a gardener can plan to set out tender crops after this day. The 50 % date, May 31, indicates the moment when a light frost is equally likely to occur later, giving a median risk perspective. A hard-frost median date, May 17, marks when a 28 °F frost is as likely as not, a threshold that can be more damaging than a 32 °F frost.

September 7 is the cautious fall date, with just a 10 % chance that a light frost has arrived earlier, allowing a gardener to finish harvesting tender crops before this point. The 50 % date, September 21, shows the median odds for a light frost earlier. A hard-frost median date, October 1, signals the 28 °F threshold, which matters more because plants that survive a light frost may still be injured by a hard frost.

How to read the probabilities

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

  • Spring: "10% after June 14" 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 7" 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 Colebrook, NHNumbered nearest stations: 1 — Island Pond, VT — 18 mi; 2 — First Connecticut Lake, NH — 20 mi; 3 — Lancaster, NH — 25 mi; 4 — York Pond, NH — 26 mi; 5 — Newport, VT — 32 mi.VTME25 mi · 40 km1. Island Pond, VT — 18 mi12. First Connecticut Lake, NH — 20 mi23. Lancaster, NH — 25 mi34. York Pond, NH — 26 mi45. Newport, VT — 32 mi5
  1. Island Pond, VT 18 mi (28 km)
  2. First Connecticut Lake, NH 20 mi (32 km)
  3. Lancaster, NH 25 mi (41 km)
  4. York Pond, NH 26 mi (43 km)
  5. Newport, VT 32 mi (52 km)

Sources

* Hardiness zone 4a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 44.8611, -71.5392.