U.S. Frost Dates by Weather Station

NOAA station USC00022754 · Arizona

Frost Dates for Duncan, AZ

NOAA weather station Duncan (USC00022754), Arizona · elevation 3660 ft (1116 m) · hardiness zone 8a*

  • Lower-risk planting dateafter May 8only 1 spring in 10 still has a frost later
  • Typical last frostApril 2450% chance of a frost after it
  • Typical first fall frostOctober 2550% chance of a frost before it
  • Frost-free season183 daystypical year, 32°F
  • Hardiness zone8acalculated*

The year at a glance

Frost season at Duncan, AZSpring: a frost after April 8 in 9 years out of 10, after April 24 in half of the years, after May 8 in 1 year out of 10. Fall: the first frost comes before October 11 in 1 year out of 10, before October 25 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 183 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 24First frost ~Oct 25Frost season at Duncan, AZSpring: a frost after April 8 in 9 years out of 10, after April 24 in half of the years, after May 8 in 1 year out of 10. Fall: the first frost comes before October 11 in 1 year out of 10, before October 25 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 183 days.JFMAMJJASONDLast frost ~Apr 24First frost ~Oct 25
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 8October 11
50% (typical)April 24October 25
90% (likely)April 8November 5
Frost-free season (32°F, 50% chance)
183 days
Hard frost (28°F), last in spring, 50% chance after
April 7
Hard frost (28°F), first in fall, 50% chance before
November 2

The last 15 years (2006–2020 normals)

Typical last frost April 24 (same as the 30-year normal), typical first fall frost October 27 (2 days later). Frost-free season 185 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 Duncan: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 8, 20% May 3, 30% April 30, 40% April 27, 50% April 24, 60% April 21, 70% April 18, 80% April 13, 90% April 8. Observed last spring frost in recent years: 2021 April 17, 2022 May 13, 2023 April 6, 2024 April 10, 2025 April 21, 2026 April 16.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 8Apr 24Apr 82021: April 172022: May 132023: April 62024: April 102025: April 212026: April 16Fall at Duncan: chance of a frost before this dateFall, chance of a frost before the date: 10% October 11, 20% October 16, 30% October 19, 40% October 22, 50% October 25, 60% October 28, 70% October 31, 80% November 1, 90% November 5. Observed first fall frost in recent years: 2021 October 13, 2022 October 25, 2023 October 31, 2024 October 20, 2025 October 30.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 11Oct 25Nov 52021: October 132022: October 252023: October 312024: October 202025: October 30
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
2021April 17October 13
2022May 13October 25
2023April 6October 31
2024April 10October 20
2025April 21October 30
2026April 16season not over yet

What these dates mean

The 183 days between the 32°F 50% dates in Duncan frame the growing window for tender crops. The 50% date in spring is April 24, a point where a light frost is equally likely to occur later, and the 50% date in fall is October 25, when a light frost is equally likely to have happened earlier.

Gardeners who prefer lower risk wait until the cautious spring date of May 8, which carries only a 10 % chance of a later frost, and they aim to finish tender harvests by the cautious fall date of October 11, which also has only a 10 % chance of an earlier frost. A hard frost, defined as 28 °F, is more damaging than a light frost, and its 50% dates are April 7 in spring and November 2 in fall, reminding that temperatures dropping to that level pose a greater risk to plant tissue.

How to read the probabilities

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

  • Spring: "10% after May 8" 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 11" 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 Duncan, AZNumbered nearest stations: 1 — San Simon, AZ — 32 mi; 2 — Safford, AZ — 33 mi; 3 — Cliff, NM — 36 mi; 4 — Animas, NM — 60 mi; 5 — Benson, AZ — 89 mi.AZNM25 mi · 40 km1. San Simon, AZ — 32 mi12. Safford, AZ — 33 mi23. Cliff, NM — 36 mi34. Animas, NM — 60 mi45. Benson, AZ — 89 mi5
  1. San Simon, AZ 32 mi (52 km)
  2. Safford, AZ 33 mi (53 km)
  3. Cliff, NM 36 mi (58 km)
  4. Animas, NM 60 mi (96 km)
  5. Benson, AZ 89 mi (143 km)

Sources

* Hardiness zone 8a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 32.7481, -109.1214.