U.S. Frost Dates by Weather Station

NOAA station USC00366233 · Pennsylvania

Frost Dates for New Castle, PA

NOAA weather station New Castle 1 N (USC00366233), Pennsylvania · elevation 825 ft (252 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 19only 1 spring in 10 still has a frost later
  • Typical last frostApril 3050% chance of a frost after it
  • Typical first fall frostOctober 2350% chance of a frost before it
  • Frost-free season175 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at New Castle, PASpring: a frost after April 17 in 9 years out of 10, after April 30 in half of the years, after May 19 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 4 in 9 years out of 10. Typical frost-free season: 175 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 30First frost ~Oct 23Frost season at New Castle, PASpring: a frost after April 17 in 9 years out of 10, after April 30 in half of the years, after May 19 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 4 in 9 years out of 10. Typical frost-free season: 175 days.JFMAMJJASONDLast frost ~Apr 30First 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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 19October 6
50% (typical)April 30October 23
90% (likely)April 17November 4
Frost-free season (32°F, 50% chance)
175 days
Hard frost (28°F), last in spring, 50% chance after
April 20
Hard frost (28°F), first in fall, 50% chance before
November 2

The last 15 years (2006–2020 normals)

Typical last frost April 30 (same as the 30-year normal), typical first fall frost October 25 (2 days later). Frost-free season 178 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 New Castle: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 19, 20% May 12, 30% May 7, 40% May 3, 50% April 30, 60% April 28, 70% April 24, 80% April 21, 90% April 17.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 19Apr 30Apr 17Fall at New Castle: chance of a frost before this dateFall, chance of a frost before the date: 10% October 6, 20% October 11, 30% October 16, 40% October 20, 50% October 23, 60% October 25, 70% October 28, 80% November 1, 90% November 4.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 6Oct 23Nov 4
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.

What these dates mean

May 19 is the cautious spring date, with only a 10% chance of a later frost, allowing a gardener to set out tender crops with low risk. The 50% spring date, April 30, marks the median point where a light frost is equally likely to occur before or after, while the 50% fall date, October 23, does the same for autumn. The hard-frost median dates are April 20 in spring and November 2 in fall, indicating when a 28 °F frost is as probable as not. A hard frost at 28 °F can damage plants more severely than a light frost at 32 °F because it reaches lower temperatures that many tender crops cannot survive. October 6 is the cautious fall date, carrying only a 10% chance that a light frost has arrived earlier, so a gardener can finish harvesting tender crops with confidence.

How to read the probabilities

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

  • Spring: "10% after May 19" 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 New Castle, PANumbered nearest stations: 1 — Slippery Rock, PA — 16 mi; 2 — Youngstown, OH — 23 mi; 3 — near Industry, PA — 26 mi; 4 — Butler, PA — 26 mi; 5 — Warren, OH — 27 mi.PAOH25 mi · 40 km1. Slippery Rock, PA — 16 mi12. Youngstown, OH — 23 mi23. near Industry, PA — 26 mi34. Butler, PA — 26 mi45. Warren, OH — 27 mi5
  1. Slippery Rock, PA 16 mi (26 km)
  2. Youngstown, OH 23 mi (37 km)
  3. near Industry, PA 26 mi (41 km)
  4. Butler, PA 26 mi (42 km)
  5. Warren, OH 27 mi (43 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: 41.0172, -80.3614.