U.S. Frost Dates by Weather Station

NOAA station USC00028619 · Arizona

Frost Dates for Tombstone, AZ

NOAA weather station Tombstone (USC00028619), Arizona · elevation 4659 ft (1420 m) · hardiness zone 9a*

  • Lower-risk planting dateafter March 31only 1 spring in 10 still has a frost later
  • Typical last frostMarch 450% chance of a frost after it
  • Typical first fall frostNovember 2950% chance of a frost before it
  • Frost-free season264 daystypical year, 32°F
  • Hardiness zone9acalculated*

The year at a glance

Frost season at Tombstone, AZSpring: a frost after February 3 in 9 years out of 10, after March 4 in half of the years, after March 31 in 1 year out of 10. Fall: the first frost comes before November 12 in 1 year out of 10, before November 29 in half of the years, before December 17 in 9 years out of 10. Typical frost-free season: 264 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Mar 4First frost ~Nov 29Frost season at Tombstone, AZSpring: a frost after February 3 in 9 years out of 10, after March 4 in half of the years, after March 31 in 1 year out of 10. Fall: the first frost comes before November 12 in 1 year out of 10, before November 29 in half of the years, before December 17 in 9 years out of 10. Typical frost-free season: 264 days.JFMAMJJASONDLast frost ~Mar 4First frost ~Nov 29
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)March 31November 12
50% (typical)March 4November 29
90% (likely)February 3December 17
Frost-free season (32°F, 50% chance)
264 days
Hard frost (28°F), last in spring, 50% chance after
February 8
Hard frost (28°F), first in fall, 50% chance before
December 12

The last 15 years (2006–2020 normals)

Typical last frost March 8 (4 days later than the 30-year normal), typical first fall frost November 30 (1 day later). Frost-free season 265 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 Tombstone: chance of a frost after this dateSpring, chance of a frost after the date: 10% March 31, 20% March 24, 30% March 16, 40% March 10, 50% March 4, 60% February 28, 70% February 23, 80% February 17, 90% February 3. Observed last spring frost in recent years: 2021 March 17, 2026 January 12.Spring: last frostChance of a frost after this date10%50%90%Feb 1Mar 1Apr 1Mar 31Mar 4Feb 32021: March 172026: January 12Fall at Tombstone: chance of a frost before this dateFall, chance of a frost before the date: 10% November 12, 20% November 18, 30% November 22, 40% November 25, 50% November 29, 60% December 2, 70% December 6, 80% December 10, 90% December 17. Observed first fall frost in recent years: 2021 December 18, 2022 November 4, 2023 November 22, 2025 January 9.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Jan 1Nov 12Nov 29Dec 172021: December 182022: November 42023: November 222025: January 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
2021March 17December 18
2022incomplete recordNovember 4
2023incomplete recordNovember 22
2024incomplete recordincomplete record
2025incomplete recordJanuary 9
2026January 12season not over yet

What these dates mean

March 31 is the cautious spring light-frost date for Tombstone, carrying only a 10 % chance that a frost will occur later; this gives a gardener enough confidence to set out tender crops at that time. The parallel cautious fall date is November 12, when there is only a 10 % chance that a frost has arrived earlier, marking a reasonable point to finish harvesting tender crops before frost becomes likely.

The 50 % light-frost date in spring is March 4, indicating a 50 % chance of a frost later than this date, while the fall 50 % date is November 29, indicating a 50 % chance of a frost earlier than this date. The median hard-frost dates are February 8 in spring and December 12 in fall; a hard frost at 28 °F can damage plants that would 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 March 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 November 12" 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 Tombstone, AZNumbered nearest stations: 1 — Benson, AZ — 15 mi; 2 — near Sierra Vista Southeast, AZ — 28 mi; 3 — near Douglas, AZ — 32 mi; 4 — near Tubac, AZ — 59 mi; 5 — San Simon, AZ — 64 mi.25 mi · 40 km1. Benson, AZ — 15 mi12. near Sierra Vista Southeast, AZ — 28 mi23. near Douglas, AZ — 32 mi34. near Tubac, AZ — 59 mi45. San Simon, AZ — 64 mi5
  1. Benson, AZ 15 mi (25 km)
  2. near Sierra Vista Southeast, AZ 28 mi (44 km)
  3. near Douglas, AZ 32 mi (52 km)
  4. near Tubac, AZ 59 mi (94 km)
  5. San Simon, AZ 64 mi (102 km)

Sources

* Hardiness zone 9a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 31.7119, -110.0686.