U.S. Frost Dates by Weather Station

NOAA station USC00366886 · Pennsylvania

Frost Dates for Phila Franklin Inst, PA

NOAA weather station Phila Franklin Inst (USC00366886), Pennsylvania · elevation 60 ft (18 m) · hardiness zone 7b*

  • Lower-risk planting dateafter April 12only 1 spring in 10 still has a frost later
  • Typical last frostMarch 3050% chance of a frost after it
  • Typical first fall frostNovember 1750% chance of a frost before it
  • Frost-free season232 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season at Phila Franklin Inst, PASpring: a frost after March 15 in 9 years out of 10, after March 30 in half of the years, after April 12 in 1 year out of 10. Fall: the first frost comes before November 4 in 1 year out of 10, before November 17 in half of the years, before December 4 in 9 years out of 10. Typical frost-free season: 232 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Mar 30First frost ~Nov 17Frost season at Phila Franklin Inst, PASpring: a frost after March 15 in 9 years out of 10, after March 30 in half of the years, after April 12 in 1 year out of 10. Fall: the first frost comes before November 4 in 1 year out of 10, before November 17 in half of the years, before December 4 in 9 years out of 10. Typical frost-free season: 232 days.JFMAMJJASONDLast frost ~Mar 30First frost ~Nov 17
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 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 12November 4
50% (typical)March 30November 17
90% (likely)March 15December 4
Frost-free season (32°F, 50% chance)
232 days
Hard frost (28°F), last in spring, 50% chance after
March 17
Hard frost (28°F), first in fall, 50% chance before
November 29

The last 15 years (2006–2020 normals)

Typical last frost March 29 (1 day earlier than the 30-year normal), typical first fall frost November 16 (1 day earlier). Frost-free season 235 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 Phila Franklin Inst: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 12, 20% April 7, 30% April 4, 40% April 1, 50% March 30, 60% March 27, 70% March 24, 80% March 20, 90% March 15. Observed last spring frost in recent years: 2021 April 4, 2022 March 30, 2023 March 20, 2024 March 24, 2025 April 9, 2026 April 9.Spring: last frostChance of a frost after this date10%50%90%Mar 1Apr 1Apr 12Mar 30Mar 152021: April 42022: March 302023: March 202024: March 242025: April 92026: April 9Fall at Phila Franklin Inst: chance of a frost before this dateFall, chance of a frost before the date: 10% November 4, 20% November 8, 30% November 11, 40% November 14, 50% November 17, 60% November 20, 70% November 23, 80% November 28, 90% December 4. Observed first fall frost in recent years: 2021 November 24, 2022 November 18, 2023 November 25, 2024 November 30, 2025 November 11.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Nov 4Nov 17Dec 42021: November 242022: November 182023: November 252024: 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 4November 24
2022March 30November 18
2023March 20November 25
2024March 24November 30
2025April 9November 11
2026April 9season not over yet

What these dates mean

The cautious spring date at Philadelphia Franklin Institute is April 12, when there is only a 10 % chance of a light frost later, allowing a gardener to set out tender crops with minimal risk. The 50% light-frost date is March 30, indicating a 50 % chance of a frost later than this day, while the 50% hard-frost date is March 17, marking a 50 % chance of a hard frost later than this day.

For fall, the cautious date is November 4, a 10 % chance of a light frost earlier, which signals when tender crops should be finished. The 50% light-frost date is November 17, giving a 50 % chance of a frost earlier than that day, and the 50% hard-frost date is November 29. Because a hard frost at 28 °F can damage vegetation that survives a light frost at 32 °F, the hard-frost dates represent a stricter threshold for protecting plants.

How to read the probabilities

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

  • Spring: "10% after April 12" 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 November 4" 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 Phila Franklin Inst, PANumbered nearest stations: 1 — Philadelphia, PA — 7 mi; 2 — Pennsauken, NJ — 8 mi; 3 — near Willingboro, NJ — 19 mi; 4 — Phoenixville, PA — 20 mi; 5 — near Wilmington, DE — 23 mi.NJMDDE25 mi · 40 km1. Philadelphia, PA — 7 mi12. Pennsauken, NJ — 8 mi23. near Willingboro, NJ — 19 mi34. Phoenixville, PA — 20 mi45. near Wilmington, DE — 23 mi5
  1. Philadelphia, PA 7 mi (11 km)
  2. Pennsauken, NJ 8 mi (13 km)
  3. near Willingboro, NJ 19 mi (31 km)
  4. Phoenixville, PA 20 mi (33 km)
  5. near Wilmington, DE 23 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: 39.9586, -75.1728.