U.S. Frost Dates by Weather Station

NOAA station USC00026468 · Arizona

Frost Dates for Petrified Forest National Park, AZ

NOAA weather station Petrified Forest National Park (USC00026468), Arizona · elevation 5446 ft (1660 m) · hardiness zone 7a*

  • Lower-risk planting dateafter May 21only 1 spring in 10 still has a frost later
  • Typical last frostMay 450% chance of a frost after it
  • Typical first fall frostOctober 1650% chance of a frost before it
  • Frost-free season162 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Petrified Forest National Park, AZSpring: a frost after April 22 in 9 years out of 10, after May 4 in half of the years, after May 21 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 16 in half of the years, before October 28 in 9 years out of 10. Typical frost-free season: 162 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 4First frost ~Oct 16Frost season at Petrified Forest National Park, AZSpring: a frost after April 22 in 9 years out of 10, after May 4 in half of the years, after May 21 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 16 in half of the years, before October 28 in 9 years out of 10. Typical frost-free season: 162 days.JFMAMJJASONDLast frost ~May 4First frost ~Oct 16
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 21October 3
50% (typical)May 4October 16
90% (likely)April 22October 28
Frost-free season (32°F, 50% chance)
162 days
Hard frost (28°F), last in spring, 50% chance after
April 24
Hard frost (28°F), first in fall, 50% chance before
October 24

The last 15 years (2006–2020 normals)

Typical last frost May 5 (1 day later than the 30-year normal), typical first fall frost October 15 (1 day earlier). Frost-free season 161 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 Petrified Forest National Park: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 21, 20% May 14, 30% May 11, 40% May 7, 50% May 4, 60% May 2, 70% April 30, 80% April 27, 90% April 22. Observed last spring frost in recent years: 2021 May 23, 2022 May 13, 2023 April 29, 2024 May 9, 2025 April 30, 2026 May 6.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 21May 4Apr 222021: May 232022: May 132023: April 292024: May 92025: April 302026: May 6Fall at Petrified Forest National Park: chance of a frost before this dateFall, chance of a frost before the date: 10% October 3, 20% October 7, 30% October 10, 40% October 13, 50% October 16, 60% October 18, 70% October 20, 80% October 23, 90% October 28. Observed first fall frost in recent years: 2021 October 13, 2022 October 24, 2023 October 13, 2024 October 21, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 3Oct 16Oct 282021: October 132022: October 242023: October 132024: October 212025: October 6
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 23October 13
2022May 13October 24
2023April 29October 13
2024May 9October 21
2025April 30October 6
2026May 6season not over yet

What these dates mean

Setting out tender crops on the early spring date of April 22 is a gamble, because there is a 90 % chance of a light frost later than that day.

The 50 % date for spring light frost is May 4, which means a 50 % chance of a frost later than this date. For fall, the 50 % date is October 16, indicating a 50 % chance of a frost earlier than this date. A cautious plan uses the May 21 date, where only a 10 % chance of a later frost exists, and the October 3 date, where only a 10 % chance of an earlier frost exists, to schedule planting and harvesting of tender crops.

Hard frosts at 28 °F, marked by the 50 % dates April 24 and October 24, can inflict far more cellular damage than light frosts at 32 °F, so they represent a higher risk for vulnerable plants.

How to read the probabilities

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

  • Spring: "10% after May 21" 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 3" 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 Petrified Forest National Park, AZNumbered nearest stations: 1 — Saint Johns, AZ — 34 mi; 2 — Show Low, AZ — 38 mi; 3 — McNary, AZ — 47 mi; 4 — Winslow, AZ — 50 mi; 5 — Springerville, AZ — 58 mi.AZNM25 mi · 40 km1. Saint Johns, AZ — 34 mi12. Show Low, AZ — 38 mi23. McNary, AZ — 47 mi34. Winslow, AZ — 50 mi45. Springerville, AZ — 58 mi5
  1. Saint Johns, AZ 34 mi (54 km)
  2. Show Low, AZ 38 mi (61 km)
  3. McNary, AZ 47 mi (76 km)
  4. Winslow, AZ 50 mi (80 km)
  5. Springerville, AZ 58 mi (93 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: 34.7994, -109.885.