U.S. Frost Dates by Weather Station

NOAA station USC00431580 · Vermont

Frost Dates for Cornwall, VT

NOAA weather station Cornwall (USC00431580), Vermont · elevation 345 ft (105 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 20only 1 spring in 10 still has a frost later
  • Typical last frostMay 550% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season151 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Cornwall, VTSpring: a frost after April 23 in 9 years out of 10, after May 5 in half of the years, after May 20 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 19 in 9 years out of 10. Typical frost-free season: 151 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 5First frost ~Oct 3Frost season at Cornwall, VTSpring: a frost after April 23 in 9 years out of 10, after May 5 in half of the years, after May 20 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 19 in 9 years out of 10. Typical frost-free season: 151 days.JFMAMJJASONDLast frost ~May 5First 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.

Frost dates (32°F)

Probability of frost, based on 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 20September 21
50% (typical)May 5October 3
90% (likely)April 23October 19
Frost-free season (32°F, 50% chance)
151 days
Hard frost (28°F), last in spring, 50% chance after
April 26
Hard frost (28°F), first in fall, 50% chance before
October 16

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 7 (4 days later). Frost-free season 154 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 Cornwall: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 20, 20% May 15, 30% May 11, 40% May 8, 50% May 5, 60% May 2, 70% April 30, 80% April 28, 90% April 23. Observed last spring frost in recent years: 2021 May 7, 2022 May 9, 2023 May 19, 2024 April 27, 2025 May 1, 2026 May 22.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 20May 5Apr 232021: May 72022: May 92023: May 192024: April 272025: May 12026: May 22Fall at Cornwall: chance of a frost before this dateFall, chance of a frost before the date: 10% September 21, 20% September 25, 30% September 29, 40% October 1, 50% October 3, 60% October 5, 70% October 8, 80% October 13, 90% October 19. Observed first fall frost in recent years: 2021 October 23, 2022 September 30, 2023 October 31, 2024 October 17, 2025 September 21.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 21Oct 3Oct 192021: October 232022: September 302023: October 312024: October 172025: 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 7October 23
2022May 9September 30
2023May 19October 31
2024April 27October 17
2025May 1September 21
2026May 22season not over yet

What these dates mean

May 20 is the cautious spring date for light frost in Cornwall, letting a gardener set out tender crops with only a 10 % chance that a frost will occur later. The 50 % date in spring is May 5; at that point there is an even chance of a frost later than the date. By contrast, April 23 carries a 90 % chance of a later frost, making a very early planting a gamble.

In fall the cautious date is September 21, when there is just a 10 % chance that a frost has already arrived, allowing the final harvest of tender crops. The 50 % date for fall is October 3, indicating an even chance of a frost earlier than that day. October 19 has a 90 % chance of an earlier frost, so waiting that long is risky. The hard-frost 50 % dates are April 26 and October 16; a hard frost at 28 °F can kill plant tissue, whereas a light frost at 32 °F merely chills it.

How to read the probabilities

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

  • Spring: "10% after May 20" 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 Cornwall, VTNumbered nearest stations: 1 — Rochester, VT — 21 mi; 2 — Rutland, VT — 26 mi; 3 — Burlington, VT — 35 mi; 4 — near Barre, VT — 36 mi; 5 — near Stowe, VT — 44 mi.NYNH25 mi · 40 km1. Rochester, VT — 21 mi12. Rutland, VT — 26 mi23. Burlington, VT — 35 mi34. near Barre, VT — 36 mi45. near Stowe, VT — 44 mi5
  1. Rochester, VT 21 mi (34 km)
  2. Rutland, VT 26 mi (41 km)
  3. Burlington, VT 35 mi (57 km)
  4. near Barre, VT 36 mi (57 km)
  5. near Stowe, VT 44 mi (71 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: 43.9572, -73.2106.