U.S. Frost Dates by Weather Station

NOAA station USW00014778 · Pennsylvania

Frost Dates for Williamsport, PA

NOAA weather station Williamsport (USW00014778), Pennsylvania · elevation 520 ft (159 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 11only 1 spring in 10 still has a frost later
  • Typical last frostApril 2450% chance of a frost after it
  • Typical first fall frostOctober 2350% chance of a frost before it
  • Frost-free season180 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Williamsport, PASpring: a frost after April 12 in 9 years out of 10, after April 24 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 23 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 180 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 24First frost ~Oct 23Frost season at Williamsport, PASpring: a frost after April 12 in 9 years out of 10, after April 24 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 23 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 180 days.JFMAMJJASONDLast frost ~Apr 24First frost ~Oct 23
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 11October 6
50% (typical)April 24October 23
90% (likely)April 12November 5
Frost-free season (32°F, 50% chance)
180 days
Hard frost (28°F), last in spring, 50% chance after
April 12
Hard frost (28°F), first in fall, 50% chance before
November 3

The last 15 years (2006–2020 normals)

Typical last frost April 22 (2 days earlier than the 30-year normal), typical first fall frost October 26 (3 days later). Frost-free season 184 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 Williamsport: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 11, 20% May 6, 30% May 1, 40% April 28, 50% April 24, 60% April 22, 70% April 19, 80% April 16, 90% April 12. Observed last spring frost in recent years: 2021 April 23, 2022 April 30, 2023 May 18, 2024 April 26, 2025 April 18, 2026 May 12.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 11Apr 24Apr 122021: April 232022: April 302023: May 182024: April 262025: April 182026: May 12Fall at Williamsport: chance of a frost before this dateFall, chance of a frost before the date: 10% October 6, 20% October 11, 30% October 15, 40% October 19, 50% October 23, 60% October 27, 70% October 30, 80% November 2, 90% November 5. Observed first fall frost in recent years: 2021 November 3, 2022 October 18, 2023 October 31, 2024 October 27, 2025 October 10.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 6Oct 23Nov 52021: November 32022: October 182023: October 312024: October 272025: October 10
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 23November 3
2022April 30October 18
2023May 18October 31
2024April 26October 27
2025April 18October 10
2026May 12season not over yet

What these dates mean

Setting out tender crops on the early spring date of April 12 in Williamsport carries a 90 % chance of a frost and is a gamble. The cautious spring date, May 11, has only a 10 % chance of a frost later, making it the low-risk choice for planting tender varieties.

The 50 % date is April 24; at that point there is a 50 % chance of a light frost later in the season. In the fall the 50 % date is October 23, when there is a 50 % chance of a light frost earlier. A cautious fall plan uses the October 6 date, which has only a 10 % chance of a frost earlier, while November 5 carries a 90 % chance and is a gamble to hold tender crops that late.

A hard frost at 28 °F, with median dates of April 12 in spring and November 3 in fall, can cause far more severe damage to plants 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 11" 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 6" 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 Williamsport, PANumbered nearest stations: 1 — Lock Haven, PA — 28 mi; 2 — Canton, PA — 28 mi; 3 — Selinsgrove, PA — 32 mi; 4 — Renovo, PA — 43 mi; 5 — Towanda, PA — 43 mi.NY25 mi · 40 km1. Lock Haven, PA — 28 mi12. Canton, PA — 28 mi23. Selinsgrove, PA — 32 mi34. Renovo, PA — 43 mi45. Towanda, PA — 43 mi5
  1. Lock Haven, PA 28 mi (45 km)
  2. Canton, PA 28 mi (46 km)
  3. Selinsgrove, PA 32 mi (51 km)
  4. Renovo, PA 43 mi (69 km)
  5. Towanda, PA 43 mi (69 km)

Sources

* Hardiness zone 6b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 41.2433, -76.9217.