U.S. Frost Dates by Weather Station

NOAA station USW00014609 · Maine

Frost Dates for Houlton, ME

NOAA weather station Houlton International Airport (USW00014609), Maine · elevation 476 ft (145 m) · hardiness zone 4b*

  • Lower-risk planting dateafter June 10only 1 spring in 10 still has a frost later
  • Typical last frostMay 2750% chance of a frost after it
  • Typical first fall frostSeptember 1850% chance of a frost before it
  • Frost-free season115 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Houlton, MESpring: a frost after May 9 in 9 years out of 10, after May 27 in half of the years, after June 10 in 1 year out of 10. Fall: the first frost comes before September 5 in 1 year out of 10, before September 18 in half of the years, before October 2 in 9 years out of 10. Typical frost-free season: 115 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 27First frost ~Sep 18Frost season at Houlton, MESpring: a frost after May 9 in 9 years out of 10, after May 27 in half of the years, after June 10 in 1 year out of 10. Fall: the first frost comes before September 5 in 1 year out of 10, before September 18 in half of the years, before October 2 in 9 years out of 10. Typical frost-free season: 115 days.JFMAMJJASONDLast frost ~May 27First frost ~Sep 18
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 10September 5
50% (typical)May 27September 18
90% (likely)May 9October 2
Frost-free season (32°F, 50% chance)
115 days
Hard frost (28°F), last in spring, 50% chance after
May 10
Hard frost (28°F), first in fall, 50% chance before
October 1

The last 15 years (2006–2020 normals)

Typical last frost May 26 (1 day earlier than the 30-year normal), typical first fall frost September 19 (1 day 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 Houlton: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 10, 20% June 5, 30% June 2, 40% May 30, 50% May 27, 60% May 25, 70% May 21, 80% May 16, 90% May 9. Observed last spring frost in recent years: 2021 May 30, 2022 May 24, 2023 May 23, 2024 May 12, 2025 May 22, 2026 June 1.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jun 10May 27May 92021: May 302022: May 242023: May 232024: May 122025: May 222026: June 1Fall at Houlton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 5, 20% September 9, 30% September 13, 40% September 16, 50% September 18, 60% September 21, 70% September 24, 80% September 28, 90% October 2. Observed first fall frost in recent years: 2021 October 4, 2022 September 30, 2023 September 26, 2024 October 8, 2025 September 20.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 5Sep 18Oct 22021: October 42022: September 302023: September 262024: October 82025: 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 4
2022May 24September 30
2023May 23September 26
2024May 12October 8
2025May 22September 20
2026June 1season not over yet

What these dates mean

The cautious fall date in Houlton for finishing the harvest is September 5, when there is only a 10 % chance that a light frost has arrived. Gardeners who wait until this date reduce the risk of frost damage to tender crops at the end of the season.

In spring the cautious date for setting out tender crops is June 10, which carries a 10 % chance of a later frost, while the 50 % date of May 27 marks the point at which light frost is equally likely to occur before or after. The 50 % light-frost dates—May 27 in spring and September 18 in fall—represent median odds, not frost thresholds. The 50 % hard-frost dates are May 10 and October 1.

A hard frost at 28 °F can injure plant tissue that would survive a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after June 10" 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 5" 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 Houlton, MENumbered nearest stations: 1 — Bridgewater, ME — 21 mi; 2 — Presque Isle, ME — 38 mi; 3 — Caribou, ME — 53 mi; 4 — Woodland, ME — 70 mi; 5 — Van Buren, ME — 72 mi.ME50 mi · 80 km1. Bridgewater, ME — 21 mi12. Presque Isle, ME — 38 mi23. Caribou, ME — 53 mi34. Woodland, ME — 70 mi45. Van Buren, ME — 72 mi5
  1. Bridgewater, ME 21 mi (34 km)
  2. Presque Isle, ME 38 mi (61 km)
  3. Caribou, ME 53 mi (85 km)
  4. Woodland, ME 70 mi (112 km)
  5. Van Buren, ME 72 mi (116 km)

Sources

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

Station coordinates: 46.1236, -67.7928.