U.S. Frost Dates by Weather Station

NOAA station USC00020683 · Arizona

Frost Dates for Benson, AZ

NOAA weather station Benson 6 SE (USC00020683), Arizona · elevation 3690 ft (1125 m) · hardiness zone 8a*

  • Lower-risk planting dateafter April 29only 1 spring in 10 still has a frost later
  • Typical last frostApril 1250% chance of a frost after it
  • Typical first fall frostNovember 150% chance of a frost before it
  • Frost-free season202 daystypical year, 32°F
  • Hardiness zone8acalculated*

The year at a glance

Frost season at Benson, AZSpring: a frost after March 26 in 9 years out of 10, after April 12 in half of the years, after April 29 in 1 year out of 10. Fall: the first frost comes before October 18 in 1 year out of 10, before November 1 in half of the years, before November 15 in 9 years out of 10. Typical frost-free season: 202 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 12First frost ~Nov 1Frost season at Benson, AZSpring: a frost after March 26 in 9 years out of 10, after April 12 in half of the years, after April 29 in 1 year out of 10. Fall: the first frost comes before October 18 in 1 year out of 10, before November 1 in half of the years, before November 15 in 9 years out of 10. Typical frost-free season: 202 days.JFMAMJJASONDLast frost ~Apr 12First frost ~Nov 1
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)April 29October 18
50% (typical)April 12November 1
90% (likely)March 26November 15
Frost-free season (32°F, 50% chance)
202 days
Hard frost (28°F), last in spring, 50% chance after
March 23
Hard frost (28°F), first in fall, 50% chance before
November 11

The last 15 years (2006–2020 normals)

Typical last frost April 8 (4 days earlier than the 30-year normal), typical first fall frost November 3 (2 days later). Frost-free season 208 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 Benson: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 29, 20% April 23, 30% April 19, 40% April 15, 50% April 12, 60% April 9, 70% April 5, 80% April 1, 90% March 26. Observed last spring frost in recent years: 2021 March 23, 2022 April 18, 2023 April 18, 2024 April 14, 2025 April 23, 2026 March 16.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 29Apr 12Mar 262021: March 232022: April 182023: April 182024: April 142025: April 232026: March 16Fall at Benson: chance of a frost before this dateFall, chance of a frost before the date: 10% October 18, 20% October 22, 30% October 26, 40% October 30, 50% November 1, 60% November 3, 70% November 7, 80% November 11, 90% November 15. Observed first fall frost in recent years: 2021 October 13, 2022 October 24, 2023 October 31, 2024 October 31, 2025 November 21.Fall: first frostChance of a frost before this date10%50%90%Nov 1Oct 18Nov 1Nov 152021: October 132022: October 242023: October 312024: October 312025: November 21
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 23October 13
2022April 18October 24
2023April 18October 31
2024April 14October 31
2025April 23November 21
2026March 16season not over yet

What these dates mean

The 202 days between the 32 °F 50 % dates in Benson bracket the period when a light frost is equally likely to occur later (spring) or earlier (fall). The 50 % spring date is April 12 and the 50 % fall date is November 1; each marks the median point at which a light frost has a 50 % chance of happening beyond that day.

For a cautious plan, tender crops should be set out after the April 29 date, which carries only a 10 % chance of a later light frost, while they should be finished by October 18, the fall date with only a 10 % chance that a light frost has arrived earlier.

A hard frost at 28 °F matters more than a light frost at 32 °F because it can freeze plant tissue that would otherwise survive a 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 April 29" 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 18" 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 Benson, AZNumbered nearest stations: 1 — Tombstone, AZ — 15 mi; 2 — near Sierra Vista Southeast, AZ — 37 mi; 3 — near Douglas, AZ — 47 mi; 4 — near Tubac, AZ — 52 mi; 5 — San Simon, AZ — 66 mi.25 mi · 40 km1. Tombstone, AZ — 15 mi12. near Sierra Vista Southeast, AZ — 37 mi23. near Douglas, AZ — 47 mi34. near Tubac, AZ — 52 mi45. San Simon, AZ — 66 mi5
  1. Tombstone, AZ 15 mi (25 km)
  2. near Sierra Vista Southeast, AZ 37 mi (60 km)
  3. near Douglas, AZ 47 mi (76 km)
  4. near Tubac, AZ 52 mi (84 km)
  5. San Simon, AZ 66 mi (106 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: 31.8806, -110.2403.