U.S. Frost Dates by Weather Station

NOAA station USC00171628 · Maine

Frost Dates for Corinna, ME

NOAA weather station Corinna (USC00171628), Maine · elevation 297 ft (91 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 23only 1 spring in 10 still has a frost later
  • Typical last frostMay 850% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season148 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Corinna, MESpring: a frost after April 27 in 9 years out of 10, after May 8 in half of the years, after May 23 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 3 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 148 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 8First frost ~Oct 3Frost season at Corinna, MESpring: a frost after April 27 in 9 years out of 10, after May 8 in half of the years, after May 23 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 3 in half of the years, before October 17 in 9 years out of 10. Typical frost-free season: 148 days.JFMAMJJASONDLast frost ~May 8First frost ~Oct 3
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.Today

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)May 23September 21
50% (typical)May 8October 3
90% (likely)April 27October 17
Frost-free season (32°F, 50% chance)
148 days
Hard frost (28°F), last in spring, 50% chance after
April 26
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 8 (same as the 30-year normal), typical first fall frost October 4 (1 day later). Frost-free season 146 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 Corinna: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 23, 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 May 8, 2022 May 9, 2023 May 18, 2024 May 10, 2025 April 24.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 23May 8Apr 272021: May 82022: May 92023: May 182024: May 102025: April 24Fall at Corinna: chance of a frost before this dateFall, chance of a frost before the date: 10% September 21, 20% September 26, 30% September 29, 40% October 1, 50% October 3, 60% October 6, 70% October 9, 80% October 12, 90% October 17. Observed first fall frost in recent years: 2021 October 24, 2022 October 3, 2023 October 24, 2024 October 16, 2025 September 21.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 21Oct 3Oct 172021: October 242022: October 32023: October 242024: October 162025: September 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. ◆ 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 8October 24
2022May 9October 3
2023May 18October 24
2024May 10October 16
2025April 24September 21
2026incomplete recordseason not over yet

What these dates mean

Between the 50% light-frost dates of May 8 and October 3, Corinna enjoys 148 days in which the chance of a light frost is less than 50 %. The 50% dates themselves are simply the points where a frost is equally likely to occur on either side, giving gardeners a rough midpoint for the frost-free season.

In spring, the cautious date for setting out tender crops is May 23, which carries only a 10 % chance of a frost later; planting on April 27 would be a gamble with a 90 % chance of frost later. In fall, the cautious date to finish harvesting tender crops is September 21, which has only a 10 % chance of a frost earlier, while October 17 would be a gamble with a 90 % chance of frost earlier. The hard-frost 50% dates are April 26 and October 15, and a hard frost at 28 °F can damage plants more severely than 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 May 23" 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 21" 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 Corinna, MENumbered nearest stations: 1 — Dover-Foxcroft, ME — 19 mi; 2 — Bangor, ME — 22 mi; 3 — Madison, ME — 33 mi; 4 — near Waterville, ME — 34 mi; 5 — Belfast, ME — 38 mi.NH25 mi · 40 km1. Dover-Foxcroft, ME — 19 mi12. Bangor, ME — 22 mi23. Madison, ME — 33 mi34. near Waterville, ME — 34 mi45. Belfast, ME — 38 mi5
  1. Dover-Foxcroft, ME 19 mi (30 km)
  2. Bangor, ME 22 mi (36 km)
  3. Madison, ME 33 mi (53 km)
  4. near Waterville, ME 34 mi (54 km)
  5. Belfast, ME 38 mi (62 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: 44.9197, -69.2417.