U.S. Frost Dates by Weather Station

NOAA station USW00013739 · Pennsylvania

Frost Dates for Philadelphia, PA

NOAA weather station Philadelphia International Airport (USW00013739), Pennsylvania · elevation 10 ft (3 m) · hardiness zone 7b*

  • Lower-risk planting dateafter April 13only 1 spring in 10 still has a frost later
  • Typical last frostApril 250% chance of a frost after it
  • Typical first fall frostNovember 1050% chance of a frost before it
  • Frost-free season224 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season at Philadelphia, PASpring: a frost after March 19 in 9 years out of 10, after April 2 in half of the years, after April 13 in 1 year out of 10. Fall: the first frost comes before October 30 in 1 year out of 10, before November 10 in half of the years, before November 24 in 9 years out of 10. Typical frost-free season: 224 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 2First frost ~Nov 10Frost season at Philadelphia, PASpring: a frost after March 19 in 9 years out of 10, after April 2 in half of the years, after April 13 in 1 year out of 10. Fall: the first frost comes before October 30 in 1 year out of 10, before November 10 in half of the years, before November 24 in 9 years out of 10. Typical frost-free season: 224 days.JFMAMJJASONDLast frost ~Apr 2First frost ~Nov 10
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)April 13October 30
50% (typical)April 2November 10
90% (likely)March 19November 24
Frost-free season (32°F, 50% chance)
224 days
Hard frost (28°F), last in spring, 50% chance after
March 22
Hard frost (28°F), first in fall, 50% chance before
November 23

The last 15 years (2006–2020 normals)

Typical last frost March 31 (2 days earlier than the 30-year normal), typical first fall frost November 13 (3 days later). Frost-free season 227 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 Philadelphia: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 13, 20% April 8, 30% April 6, 40% April 3, 50% April 2, 60% March 31, 70% March 29, 80% March 24, 90% March 19. Observed last spring frost in recent years: 2021 April 3, 2022 April 18, 2023 March 21, 2024 March 24, 2025 March 9, 2026 April 8.Spring: last frostChance of a frost after this date10%50%90%Apr 1Apr 13Apr 2Mar 192021: April 32022: April 182023: March 212024: March 242025: March 92026: April 8Fall at Philadelphia: chance of a frost before this dateFall, chance of a frost before the date: 10% October 30, 20% November 2, 30% November 5, 40% November 8, 50% November 10, 60% November 13, 70% November 16, 80% November 19, 90% November 24. Observed first fall frost in recent years: 2021 November 17, 2022 November 18, 2023 November 13, 2024 November 30, 2025 November 11.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 30Nov 10Nov 242021: November 172022: November 182023: November 132024: November 302025: November 11
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
2021April 3November 17
2022April 18November 18
2023March 21November 13
2024March 24November 30
2025March 9November 11
2026April 8season not over yet

What these dates mean

April 13 is the cautious spring date for light frost in Philadelphia; with only a 10 % chance of a frost later than that day, a gardener can plan to set out tender crops after it. By contrast, the March 19 date carries a 90 % chance of a later frost, making an earlier planting a gamble.

The median 32 °F dates are April 2 in spring and November 10 in fall, each representing a 50 % chance of a light frost occurring after (spring) or before (fall) the date. The 28 °F hard-frost medians are March 22 and November 23; these indicate when a hard frost is as likely as not. For a conservative fall schedule, the October 30 date—only a 10 % chance of a frost earlier—guides the latest time to finish harvesting tender crops.

A hard frost can damage plants that survive a light frost, so it matters more for garden survival.

How to read the probabilities

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

  • Spring: "10% after April 13" 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 October 30" 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 Philadelphia, PANumbered nearest stations: 1 — Phila Franklin Inst, PA — 7 mi; 2 — Pennsauken, NJ — 13 mi; 3 — near Wilmington, DE — 18 mi; 4 — Phoenixville, PA — 22 mi; 5 — near Wilmington Manor, DE — 24 mi.PAMDDE25 mi · 40 km1. Phila Franklin Inst, PA — 7 mi12. Pennsauken, NJ — 13 mi23. near Wilmington, DE — 18 mi34. Phoenixville, PA — 22 mi45. near Wilmington Manor, DE — 24 mi5
  1. Phila Franklin Inst, PA 7 mi (11 km)
  2. Pennsauken, NJ 13 mi (21 km)
  3. near Wilmington, DE 18 mi (29 km)
  4. Phoenixville, PA 22 mi (36 km)
  5. near Wilmington Manor, DE 24 mi (38 km)

Sources

* Hardiness zone 7b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 39.8683, -75.2311.