U.S. Frost Dates by Weather Station

NOAA station USC00170844 · Maine

Frost Dates for Bridgton, ME

NOAA weather station Bridgton 3 NW (USC00170844), Maine · elevation 508 ft (155 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 550% chance of a frost after it
  • Typical first fall frostOctober 550% chance of a frost before it
  • Frost-free season151 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Bridgton, MESpring: a frost after April 26 in 9 years out of 10, after May 5 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 5 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 151 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 5First frost ~Oct 5Frost season at Bridgton, MESpring: a frost after April 26 in 9 years out of 10, after May 5 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 22 in 1 year out of 10, before October 5 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 151 days.JFMAMJJASONDLast frost ~May 5First frost ~Oct 5
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 22
50% (typical)May 5October 5
90% (likely)April 26October 21
Frost-free season (32°F, 50% chance)
151 days
Hard frost (28°F), last in spring, 50% chance after
April 25
Hard frost (28°F), first in fall, 50% chance before
October 19

The last 15 years (2006–2020 normals)

Typical last frost May 3 (2 days earlier than the 30-year normal), typical first fall frost October 10 (5 days later). Frost-free season 158 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 Bridgton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 13, 30% May 10, 40% May 8, 50% May 5, 60% May 3, 70% May 2, 80% April 30, 90% April 26.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 5Apr 26Fall at Bridgton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 22, 20% September 26, 30% October 1, 40% October 2, 50% October 5, 60% October 7, 70% October 10, 80% October 15, 90% October 21.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 22Oct 5Oct 21
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.

What these dates mean

The cautious fall date for finishing the harvest in Bridgton is September 22, when there is only a 10 % chance that a light frost has already arrived. In spring the 50 % date is May 5, marking an even chance of a light frost, while the 50 % date in fall is October 5, also an even chance. The 50 % hard-frost dates are April 25 in spring and October 19 in fall, indicating the midpoint where a 28 °F frost is equally likely to have occurred or not.

The cautious plan for tender crops uses the May 17 date in spring, which carries a 10 % chance of a later frost, and the September 22 date in fall, which similarly offers only a 10 % chance that a frost has come earlier.

Hard frost at 28 °F can injure plants that would survive a 32 °F light frost, making it a more critical threshold.

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 22" 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 Bridgton, MENumbered nearest stations: 1 — North Conway, NH — 19 mi; 2 — Gray, ME — 27 mi; 3 — Pinkham Notch, NH — 28 mi; 4 — Berlin, NH — 34 mi; 5 — Portland, ME — 37 mi.MENHVT25 mi · 40 km1. North Conway, NH — 19 mi12. Gray, ME — 27 mi23. Pinkham Notch, NH — 28 mi34. Berlin, NH — 34 mi45. Portland, ME — 37 mi5
  1. North Conway, NH 19 mi (31 km)
  2. Gray, ME 27 mi (44 km)
  3. Pinkham Notch, NH 28 mi (45 km)
  4. Berlin, NH 34 mi (55 km)
  5. Portland, ME 37 mi (59 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: 44.07, -70.7467.