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USDA hardiness zone lookup

Phoenix, AZ — USDA Zone 9b

Phoenix, Arizona · 299-day growing season

Frost dates and growing season in Phoenix

USDA hardiness zoneZone 9b
Average last spring frostFebruary 5
Average first fall frostDecember 1
Growing season length~299 days
Temperature range (F)20 to 30°F
Temperature range (C)-7 to -1°C

Phoenix spans USDA zones 9 to 10 across its ZIP codes (Zone 10a, Zone 9b); the city center sits in Zone 9b, so warmer and cooler pockets exist either side of that.

These are 50%-probability averages modeled from Phoenix's USDA hardiness zone and regional climate normals — not a single-station reading. In a typical year the last spring frost will have passed by February 5, but a colder-than-average year can run 1-2 weeks later. Plant tender crops (tomatoes, peppers, basil) once both soil and night temperatures are consistently warm — a thermometer beats the calendar.

Growing season in Phoenix

Phoenix, Arizona sits in USDA Zone 9b, with roughly 299 frost-free days between an average last spring frost around February 5 and a first fall frost around December 1. That is a near year-round season — the limiting factor is summer heat, not frost, so schedule cool-season crops for winter and protect tender ones from extreme highs. Phoenix lies near 33.4°N; higher-latitude gardens get longer midsummer days but a tighter shoulder season at this zone. As a large metro, the built-up core typically runs up to half a zone warmer than outlying suburbs through the urban heat-island effect — sheltered city gardens often push tender crops a little earlier than the average suggests.

What grows in Phoenix

Phoenix falls in USDA Zone 9b, so the same hardiness constraints apply as the full Zone 9 guide. Vegetables, herbs, and fruit trees rated to Zone 9b (or hardier) will overwinter here in a typical year.

What to plant in Phoenix this week

Phoenix is in high summer — most spring plantings are in. Keep an eye on watering and start planning your fall crop. Cool-season seedlings (broccoli, cabbage, lettuce) can be started indoors for a fall transplant.

Full planting calendar for Phoenix

Crop-by-crop sowing, transplant, and harvest dates calibrated to zone 9 averages:

ZIP codes in Phoenix

Drill down to the precise frost window and planting calendar for a specific ZIP in Phoenix:

Local microclimate notes

Zone tables give you the average — but Phoenixgardens vary. South-facing walls and paved areas can run a full half-zone warmer than the published rating. Low-lying spots, frost pockets, and shaded north sides can run colder. If you've gardened here a few seasons, your own frost record — the last time you actually got frost damage — beats any national average.

Source and methodology

Hardiness zone from the USDA Plant Hardiness Zone Map (2023 revision). Frost-date and growing-season figures are modeled from Phoenix's USDA hardiness zone and regional NOAA 1991-2020 climate normals — zone-level estimates, not a per-station record, so treat them as planning guidance and confirm against your own local frost history. Crop recommendations draw on US Cooperative Extension references, curated by the Growli editorial team. Last reviewed June 2026.

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