U.S. Frost Dates by Weather Station

NOAA station USC00369298 · Pennsylvania

Frost Dates for Warren, PA

NOAA weather station Warren (USC00369298), Pennsylvania · elevation 1210 ft (369 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 22only 1 spring in 10 still has a frost later
  • Typical last frostMay 450% chance of a frost after it
  • Typical first fall frostOctober 2150% chance of a frost before it
  • Frost-free season168 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Warren, PASpring: a frost after April 20 in 9 years out of 10, after May 4 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 21 in half of the years, before November 4 in 9 years out of 10. Typical frost-free season: 168 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 4First frost ~Oct 21Frost season at Warren, PASpring: a frost after April 20 in 9 years out of 10, after May 4 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 21 in half of the years, before November 4 in 9 years out of 10. Typical frost-free season: 168 days.JFMAMJJASONDLast frost ~May 4First frost ~Oct 21
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 22October 6
50% (typical)May 4October 21
90% (likely)April 20November 4
Frost-free season (32°F, 50% chance)
168 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
November 2

The last 15 years (2006–2020 normals)

Typical last frost May 2 (2 days earlier than the 30-year normal), typical first fall frost October 22 (1 day later). Frost-free season 170 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 Warren: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 22, 20% May 16, 30% May 11, 40% May 7, 50% May 4, 60% April 30, 70% April 28, 80% April 24, 90% April 20. Observed last spring frost in recent years: 2021 May 2, 2022 May 1, 2023 May 18, 2024 April 27, 2025 April 18, 2026 May 13.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 22May 4Apr 202021: May 22022: May 12023: May 182024: April 272025: April 182026: May 13Fall at Warren: chance of a frost before this dateFall, chance of a frost before the date: 10% October 6, 20% October 11, 30% October 14, 40% October 18, 50% October 21, 60% October 24, 70% October 27, 80% October 31, 90% November 4. Observed first fall frost in recent years: 2021 November 4, 2022 October 16, 2023 October 23, 2024 October 17, 2025 October 17.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 6Oct 21Nov 42021: November 42022: October 162023: October 232024: October 172025: October 17
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 2November 4
2022May 1October 16
2023May 18October 23
2024April 27October 17
2025April 18October 17
2026May 13season not over yet

What these dates mean

The 168 days between the 50% dates in Warren, Pennsylvania, mark the central window that gardeners use to schedule planting and harvesting of tender crops. The 50% date of May 4 marks the point at which there is an even chance of a light frost having occurred, while the 50% date of October 21 represents the same even odds later in the season.

A cautious plan for tender crops in spring waits until the May 22 date, which carries only a 10 % chance of a light frost later than that day. In the fall, the cautious date is October 6, with a 10 % chance of a light frost earlier than that day. The hard-frost 50% dates—April 23 in spring and November 2 in fall—show where a 28 °F frost is equally likely to have occurred, and a hard frost can damage plants more severely than a light frost because it reaches a lower temperature threshold.

How to read the probabilities

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

  • Spring: "10% after May 22" 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 Warren, PANumbered nearest stations: 1 — Jamestown, NY — 18 mi; 2 — Kane, PA — 21 mi; 3 — Bradford 4 SW Research 5, PA — 23 mi; 4 — Bradford, PA — 26 mi; 5 — near Allegany, NY — 27 mi.NY25 mi · 40 km1. Jamestown, NY — 18 mi12. Kane, PA — 21 mi23. Bradford 4 SW Research 5, PA — 23 mi34. Bradford, PA — 26 mi45. near Allegany, NY — 27 mi5
  1. Jamestown, NY 18 mi (29 km)
  2. Kane, PA 21 mi (34 km)
  3. Bradford 4 SW Research 5, PA 23 mi (36 km)
  4. Bradford, PA 26 mi (42 km)
  5. near Allegany, NY 27 mi (43 km)

Sources

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

Station coordinates: 41.8467, -79.1494.