U.S. Frost Dates by Weather Station

NOAA station USC00027435 · Arizona

Frost Dates for Saint Johns, AZ

NOAA weather station Saint Johns (USC00027435), Arizona · elevation 5790 ft (1765 m) · hardiness zone 7a*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 1450% chance of a frost before it
  • Frost-free season164 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Saint Johns, AZSpring: a frost after April 18 in 9 years out of 10, after May 2 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 14 in half of the years, before October 27 in 9 years out of 10. Typical frost-free season: 164 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 14Frost season at Saint Johns, AZSpring: a frost after April 18 in 9 years out of 10, after May 2 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before October 3 in 1 year out of 10, before October 14 in half of the years, before October 27 in 9 years out of 10. Typical frost-free season: 164 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 14
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 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 17October 3
50% (typical)May 2October 14
90% (likely)April 18October 27
Frost-free season (32°F, 50% chance)
164 days
Hard frost (28°F), last in spring, 50% chance after
April 19
Hard frost (28°F), first in fall, 50% chance before
October 23

The last 15 years (2006–2020 normals)

Typical last frost May 2 (same as the 30-year normal), typical first fall frost October 15 (1 day later). Frost-free season 164 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 Saint Johns: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 12, 30% May 7, 40% May 5, 50% May 2, 60% April 30, 70% April 26, 80% April 23, 90% April 18. Observed last spring frost in recent years: 2021 April 19, 2022 April 25, 2023 April 29, 2024 April 16, 2025 April 30, 2026 April 18.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 2Apr 182021: April 192022: April 252023: April 292024: April 162025: April 302026: April 18Fall at Saint Johns: chance of a frost before this dateFall, chance of a frost before the date: 10% October 3, 20% October 6, 30% October 9, 40% October 12, 50% October 14, 60% October 17, 70% October 19, 80% October 22, 90% October 27. Observed first fall frost in recent years: 2021 October 11, 2022 October 24, 2023 October 15, 2024 October 19, 2025 October 29.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 3Oct 14Oct 272021: October 112022: October 242023: October 152024: October 192025: October 29
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 19October 11
2022April 25October 24
2023April 29October 15
2024April 16October 19
2025April 30October 29
2026April 18season not over yet

What these dates mean

The cautious fall date for finishing the harvest in Saint Johns is October 3, when there is only a 10 % chance that a light frost has already arrived. For a gardener, the 50 % light-frost dates—May 2 in spring and October 14 in fall—mark the points at which the odds of a frost are even, giving a neutral reference for planning. The cautious spring date for setting out tender crops is May 17, which carries only a 10 % chance of a frost later.

Hard-frost 50 % dates are April 19 in spring and October 23 in fall, indicating when a 28 °F frost is as likely as not. A hard frost at 28 °F can damage plants that survive a light frost at 32 °F, making it a more critical threshold.

How to read the probabilities

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

  • Spring: "10% after May 17" 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 Saint Johns, AZNumbered nearest stations: 1 — Springerville, AZ — 28 mi; 2 — Petrified Forest National Park, AZ — 34 mi; 3 — McNary, AZ — 38 mi; 4 — Show Low, AZ — 39 mi; 5 — Zuni, NM — 50 mi.AZNM25 mi · 40 km1. Springerville, AZ — 28 mi12. Petrified Forest National Park, AZ — 34 mi23. McNary, AZ — 38 mi34. Show Low, AZ — 39 mi45. Zuni, NM — 50 mi5
  1. Springerville, AZ 28 mi (45 km)
  2. Petrified Forest National Park, AZ 34 mi (54 km)
  3. McNary, AZ 38 mi (61 km)
  4. Show Low, AZ 39 mi (62 km)
  5. Zuni, NM 50 mi (80 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: 34.5172, -109.4028.