U.S. Frost Dates by Weather Station

NOAA station USC00360140 · Pennsylvania

Frost Dates for Altoona, PA

NOAA weather station Altoona 3 W (USC00360140), Pennsylvania · elevation 1320 ft (402 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 11only 1 spring in 10 still has a frost later
  • Typical last frostApril 2550% chance of a frost after it
  • Typical first fall frostOctober 2150% chance of a frost before it
  • Frost-free season176 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Altoona, PASpring: a frost after April 10 in 9 years out of 10, after April 25 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 5 in 1 year out of 10, before October 21 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 176 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 25First frost ~Oct 21Frost season at Altoona, PASpring: a frost after April 10 in 9 years out of 10, after April 25 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 5 in 1 year out of 10, before October 21 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 176 days.JFMAMJJASONDLast frost ~Apr 25First 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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 11October 5
50% (typical)April 25October 21
90% (likely)April 10November 5
Frost-free season (32°F, 50% chance)
176 days
Hard frost (28°F), last in spring, 50% chance after
April 13
Hard frost (28°F), first in fall, 50% chance before
November 3

The last 15 years (2006–2020 normals)

Typical last frost April 26 (1 day later than the 30-year normal), typical first fall frost October 25 (4 days later). Frost-free season 180 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 Altoona: 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 29, 50% April 25, 60% April 22, 70% April 19, 80% April 15, 90% April 10. Observed last spring frost in recent years: 2021 May 12, 2022 May 1, 2023 April 25, 2024 April 21, 2025 April 17, 2026 May 3.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 11Apr 25Apr 102021: May 122022: May 12023: April 252024: April 212025: April 172026: May 3Fall at Altoona: chance of a frost before this dateFall, chance of a frost before the date: 10% October 5, 20% October 10, 30% October 15, 40% October 18, 50% October 21, 60% October 24, 70% October 27, 80% November 1, 90% November 5. Observed first fall frost in recent years: 2021 November 2, 2022 October 20, 2023 October 31, 2024 October 17, 2025 October 26.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 5Oct 21Nov 52021: November 22022: October 202023: October 312024: October 172025: 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
2021May 12November 2
2022May 1October 20
2023April 25October 31
2024April 21October 17
2025April 17October 26
2026May 3season not over yet

What these dates mean

Planting tender crops on April 10 in Altoona carries a 90 % chance that a light frost will still occur later that season, so it is a gamble. The cautious spring date for setting out those crops is May 11, when only a 10 % chance of a later frost remains. In the fall, the cautious date to finish harvesting tender crops is October 5, with only a 10 % chance that a frost has already arrived, while waiting until November 5 would be a gamble because a frost is 90 % likely earlier.

The 50 % dates mark the point of even odds: the spring 32 °F median is April 25, at which there is a 50 % chance of a light frost later, and the fall 32 °F median is October 21, when there is a 50 % chance of a light frost earlier. Hard-frost median dates are April 13 and November 3; a 28 °F frost can damage plants more severely than a 32 °F light frost.

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 5" 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 Altoona, PANumbered nearest stations: 1 — near Patton, PA — 12 mi; 2 — Ebensburg, PA — 14 mi; 3 — near Martinsburg, PA — 16 mi; 4 — Everett, PA — 34 mi; 5 — Indiana, PA — 35 mi.MD25 mi · 40 km1. near Patton, PA — 12 mi12. Ebensburg, PA — 14 mi23. near Martinsburg, PA — 16 mi34. Everett, PA — 34 mi45. Indiana, PA — 35 mi5
  1. near Patton, PA 12 mi (19 km)
  2. Ebensburg, PA 14 mi (23 km)
  3. near Martinsburg, PA 16 mi (25 km)
  4. Everett, PA 34 mi (54 km)
  5. Indiana, PA 35 mi (56 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: 40.495, -78.4667.