U.S. Frost Dates by Weather Station

NOAA station USW00014606 · Maine

Frost Dates for Bangor, ME

NOAA weather station Bangor International Airport (USW00014606), Maine · elevation 148 ft (45 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 450% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season152 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Bangor, MESpring: a frost after April 24 in 9 years out of 10, after May 4 in half of the years, after May 17 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 21 in 9 years out of 10. Typical frost-free season: 152 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 4First frost ~Oct 4Frost season at Bangor, MESpring: a frost after April 24 in 9 years out of 10, after May 4 in half of the years, after May 17 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 21 in 9 years out of 10. Typical frost-free season: 152 days.JFMAMJJASONDLast frost ~May 4First 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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 17September 23
50% (typical)May 4October 4
90% (likely)April 24October 21
Frost-free season (32°F, 50% chance)
152 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost May 3 (1 day earlier than the 30-year normal), typical first fall frost October 8 (4 days later). Frost-free season 155 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 Bangor: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 13, 30% May 9, 40% May 7, 50% May 4, 60% May 2, 70% April 30, 80% April 27, 90% April 24. Observed last spring frost in recent years: 2021 May 7, 2022 May 8, 2023 May 18, 2024 May 10, 2025 April 21, 2026 May 12.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 4Apr 242021: May 72022: May 82023: May 182024: May 102025: April 212026: May 12Fall at Bangor: chance of a frost before this dateFall, chance of a frost before the date: 10% September 23, 20% September 27, 30% September 30, 40% October 2, 50% October 4, 60% October 7, 70% October 10, 80% October 14, 90% October 21. Observed first fall frost in recent years: 2021 November 3, 2022 October 2, 2023 October 30, 2024 October 17, 2025 October 2.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 23Oct 4Oct 212021: November 32022: October 22023: October 302024: October 172025: October 2
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 7November 3
2022May 8October 2
2023May 18October 30
2024May 10October 17
2025April 21October 2
2026May 12season not over yet

What these dates mean

September 23 is the cautious fall date for finishing the harvest in Bangor, carrying only a 10 % chance that a light frost has arrived earlier.

For a cautious spring plan, May 17 is used, because there is only a 10 % chance of a light frost later than that day. The 50 % date in spring is May 4, indicating an even chance of a light frost occurring later, while the 50 % date in fall is October 4, indicating an even chance of a light frost occurring earlier. Gardeners who follow the cautious dates aim to set out tender crops after May 17 and to finish harvesting before September 23.

Hard-frost dates, April 23 and October 17, mark when a 28 °F frost has a 50 % chance, and such a hard frost can damage plants that survive a 32 °F light frost.

How to read the probabilities

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

  • Spring: "10% after May 17" 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 Bangor, MENumbered nearest stations: 1 — Corinna, ME — 22 mi; 2 — Belfast, ME — 29 mi; 3 — Dover-Foxcroft, ME — 32 mi; 4 — West Rockport, ME — 45 mi; 5 — near Waterville, ME — 45 mi.25 mi · 40 km1. Corinna, ME — 22 mi12. Belfast, ME — 29 mi23. Dover-Foxcroft, ME — 32 mi34. West Rockport, ME — 45 mi45. near Waterville, ME — 45 mi5
  1. Corinna, ME 22 mi (36 km)
  2. Belfast, ME 29 mi (47 km)
  3. Dover-Foxcroft, ME 32 mi (52 km)
  4. West Rockport, ME 45 mi (72 km)
  5. near Waterville, ME 45 mi (73 km)

Sources

* Hardiness zone 5a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 44.7978, -68.8186.