U.S. Frost Dates by Weather Station

NOAA station USC00437054 · Vermont

Frost Dates for Saint Johnsbury, VT

NOAA weather station Saint Johnsbury (USC00437054), Vermont · elevation 700 ft (213 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 25only 1 spring in 10 still has a frost later
  • Typical last frostMay 1350% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season143 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Saint Johnsbury, VTSpring: a frost after April 30 in 9 years out of 10, after May 13 in half of the years, after May 25 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 16 in 9 years out of 10. Typical frost-free season: 143 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 13First frost ~Oct 3Frost season at Saint Johnsbury, VTSpring: a frost after April 30 in 9 years out of 10, after May 13 in half of the years, after May 25 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 16 in 9 years out of 10. Typical frost-free season: 143 days.JFMAMJJASONDLast frost ~May 13First 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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 25September 21
50% (typical)May 13October 3
90% (likely)April 30October 16
Frost-free season (32°F, 50% chance)
143 days
Hard frost (28°F), last in spring, 50% chance after
May 1
Hard frost (28°F), first in fall, 50% chance before
October 13

The last 15 years (2006–2020 normals)

Typical last frost May 10 (3 days earlier than the 30-year normal), typical first fall frost October 5 (2 days later). Frost-free season 148 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 Saint Johnsbury: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 25, 20% May 21, 30% May 19, 40% May 16, 50% May 13, 60% May 10, 70% May 8, 80% May 4, 90% April 30. Observed last spring frost in recent years: 2021 May 7, 2022 May 9, 2023 May 26, 2024 April 27, 2025 May 1, 2026 May 22.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 25May 13Apr 302021: May 72022: May 92023: May 262024: April 272025: May 12026: May 22Fall at Saint Johnsbury: 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 5, 70% October 8, 80% October 11, 90% October 16. Observed first fall frost in recent years: 2021 October 23, 2022 October 3, 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 162021: October 232022: October 32023: 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 9October 3
2023May 26October 31
2024April 27October 17
2025May 1September 21
2026May 22season not over yet

What these dates mean

The 143 days between the 50% dates in Saint Johnsbury, May 13 and October 3, define the period when light frost is no more likely than not. During this interval gardeners can expect a roughly equal chance of frost each day, and it marks the core of the growing season.

For tender crops the cautious spring date is May 25, when there is only a 10% chance of a later light frost; planting earlier, such as on April 30, carries a 90% chance of a frost and is a gamble. In the fall the cautious date to finish harvesting tender crops is September 21, with a 10% chance that a light frost has already arrived; extending harvest to October 16 faces a 90% chance of a frost and is risky.

A hard frost, recorded by the 50% hard-frost dates of May 1 and October 13, can damage plants more severely than a light frost because temperatures drop below 28 °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 25" 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 Saint Johnsbury, VTNumbered nearest stations: 1 — Lancaster, NH — 22 mi; 2 — Island Pond, VT — 28 mi; 3 — near Barre, VT — 31 mi; 4 — York Pond, NH — 34 mi; 5 — Newport, VT — 38 mi.VTMENY25 mi · 40 km1. Lancaster, NH — 22 mi12. Island Pond, VT — 28 mi23. near Barre, VT — 31 mi34. York Pond, NH — 34 mi45. Newport, VT — 38 mi5
  1. Lancaster, NH 22 mi (36 km)
  2. Island Pond, VT 28 mi (45 km)
  3. near Barre, VT 31 mi (51 km)
  4. York Pond, NH 34 mi (55 km)
  5. Newport, VT 38 mi (60 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: 44.42, -72.0194.