U.S. Frost Dates by Weather Station

NOAA station USC00360868 · Pennsylvania

Frost Dates for Bradford 4 SW Research 5, PA

NOAA weather station Bradford 4 SW Research 5 (USC00360868), Pennsylvania · elevation 1660 ft (506 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 31only 1 spring in 10 still has a frost later
  • Typical last frostMay 1850% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season140 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Bradford 4 SW Research 5, PASpring: a frost after April 30 in 9 years out of 10, after May 18 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 140 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 18First frost ~Oct 4Frost season at Bradford 4 SW Research 5, PASpring: a frost after April 30 in 9 years out of 10, after May 18 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 140 days.JFMAMJJASONDLast frost ~May 18First frost ~Oct 4
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 31September 21
50% (typical)May 18October 4
90% (likely)April 30October 19
Frost-free season (32°F, 50% chance)
140 days
Hard frost (28°F), last in spring, 50% chance after
May 4
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost May 13 (5 days earlier than the 30-year normal), typical first fall frost October 10 (6 days later). Frost-free season 147 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 Bradford 4 SW Research 5: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 31, 20% May 27, 30% May 24, 40% May 21, 50% May 18, 60% May 15, 70% May 11, 80% May 6, 90% April 30. Observed last spring frost in recent years: 2021 May 15, 2022 May 9, 2023 May 26, 2024 April 27, 2025 June 2, 2026 May 13.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 31May 18Apr 302021: May 152022: May 92023: May 262024: April 272025: June 22026: May 13Fall at Bradford 4 SW Research 5: chance of a frost before this dateFall, chance of a frost before the date: 10% September 21, 20% September 26, 30% September 29, 40% October 1, 50% October 4, 60% October 7, 70% October 10, 80% October 14, 90% October 19. Observed first fall frost in recent years: 2021 October 28, 2022 October 3, 2023 October 19, 2024 October 11, 2025 October 9.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 21Oct 4Oct 192021: October 282022: October 32023: October 192024: October 112025: October 9
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
2021May 15October 28
2022May 9October 3
2023May 26October 19
2024April 27October 11
2025June 2October 9
2026May 13season not over yet

What these dates mean

The 140 days between the 32°F 50% dates, May 18 and October 4, mark the span when a light frost is less likely than not for Bradford 4 SW Research 5. The 50% dates themselves signal an even chance of a frost occurring later (spring) or earlier (fall), giving gardeners a statistical midpoint for planning.

For a cautious spring schedule, the 10% chance date of May 31 is the point at which tender crops can be set out with only a small risk of a later light frost. In the fall, September 21 serves as the cautious date to finish harvesting tender crops, carrying only a 10% chance that a light frost has already arrived. The hard-frost 50% dates, May 4 and October 17, indicate when a 28 °F event is equally likely to have happened or not; a hard frost can damage plants that would otherwise survive 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 31" 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 September 21" 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 Bradford 4 SW Research 5, PANumbered nearest stations: 1 — Bradford, PA — 8 mi; 2 — near Allegany, NY — 14 mi; 3 — Kane, PA — 16 mi; 4 — Warren, PA — 23 mi; 5 — Little Valley, NY — 25 mi.NY25 mi · 40 km1. Bradford, PA — 8 mi12. near Allegany, NY — 14 mi23. Kane, PA — 16 mi34. Warren, PA — 23 mi45. Little Valley, NY — 25 mi5
  1. Bradford, PA 8 mi (12 km)
  2. near Allegany, NY 14 mi (23 km)
  3. Kane, PA 16 mi (26 km)
  4. Warren, PA 23 mi (36 km)
  5. Little Valley, NY 25 mi (40 km)

Sources

* Hardiness zone 5b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 41.8981, -78.7144.