U.S. Frost Dates by Weather Station

NOAA station USC00364992 · Pennsylvania

Frost Dates for Lewistown, PA

NOAA weather station Lewistown (USC00364992), Pennsylvania · elevation 460 ft (140 m) · hardiness zone 7a*

  • Lower-risk planting dateafter May 9only 1 spring in 10 still has a frost later
  • Typical last frostApril 2150% chance of a frost after it
  • Typical first fall frostOctober 2450% chance of a frost before it
  • Frost-free season185 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Lewistown, PASpring: a frost after April 6 in 9 years out of 10, after April 21 in half of the years, after May 9 in 1 year out of 10. Fall: the first frost comes before October 7 in 1 year out of 10, before October 24 in half of the years, before November 7 in 9 years out of 10. Typical frost-free season: 185 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 21First frost ~Oct 24Frost season at Lewistown, PASpring: a frost after April 6 in 9 years out of 10, after April 21 in half of the years, after May 9 in 1 year out of 10. Fall: the first frost comes before October 7 in 1 year out of 10, before October 24 in half of the years, before November 7 in 9 years out of 10. Typical frost-free season: 185 days.JFMAMJJASONDLast frost ~Apr 21First frost ~Oct 24
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 9October 7
50% (typical)April 21October 24
90% (likely)April 6November 7
Frost-free season (32°F, 50% chance)
185 days
Hard frost (28°F), last in spring, 50% chance after
April 6
Hard frost (28°F), first in fall, 50% chance before
November 5

The last 15 years (2006–2020 normals)

Typical last frost April 18 (3 days earlier than the 30-year normal), typical first fall frost October 29 (5 days later). Frost-free season 192 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 Lewistown: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 9, 20% May 1, 30% April 28, 40% April 24, 50% April 21, 60% April 18, 70% April 15, 80% April 11, 90% April 6. Observed last spring frost in recent years: 2021 April 23, 2022 May 1, 2023 April 26, 2024 April 23, 2025 April 18, 2026 April 22.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 9Apr 21Apr 62021: April 232022: May 12023: April 262024: April 232025: April 182026: April 22Fall at Lewistown: chance of a frost before this dateFall, chance of a frost before the date: 10% October 7, 20% October 13, 30% October 17, 40% October 21, 50% October 24, 60% October 27, 70% October 31, 80% November 2, 90% November 7. Observed first fall frost in recent years: 2021 September 26, 2022 October 21, 2023 November 1, 2024 October 28, 2025 October 26.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 7Oct 24Nov 72021: September 262022: October 212023: November 12024: October 282025: October 26
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 23September 26
2022May 1October 21
2023April 26November 1
2024April 23October 28
2025April 18October 26
2026April 22season not over yet

What these dates mean

Setting out tender crops on the early spring date, April 6, carries a 90% chance of a frost later that season, making it a gamble for Lewistown gardeners. A more cautious plan would wait until the May 9 date, when only a 10% chance of a later frost remains.

In the fall, the cautious date to finish harvesting tender crops is October 7, which bears a 10% chance of an earlier frost; waiting until November 7 would be a gamble with a 90% chance of frost already having arrived. The 50% date is April 21, indicating an even likelihood of a frost later than this date in spring, while the 50% date is October 24, indicating an even likelihood of a frost earlier than this date in fall.

Hard frost at 28 °F can damage plants that survive a light frost at 32 °F, so the 28 °F threshold is more critical for garden planning.

How to read the probabilities

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

  • Spring: "10% after May 9" 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 7" 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 Lewistown, PANumbered nearest stations: 1 — State College, PA — 21 mi; 2 — Shippensburg, PA — 37 mi; 3 — Lock Haven, PA — 38 mi; 4 — Selinsgrove, PA — 39 mi; 5 — near Martinsburg, PA — 44 mi.25 mi · 40 km1. State College, PA — 21 mi12. Shippensburg, PA — 37 mi23. Lock Haven, PA — 38 mi34. Selinsgrove, PA — 39 mi45. near Martinsburg, PA — 44 mi5
  1. State College, PA 21 mi (34 km)
  2. Shippensburg, PA 37 mi (59 km)
  3. Lock Haven, PA 38 mi (62 km)
  4. Selinsgrove, PA 39 mi (64 km)
  5. near Martinsburg, PA 44 mi (71 km)

Sources

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

Station coordinates: 40.5864, -77.5692.