What does USDA hardiness zone 5b mean in Arizona?

Zone 5b means an average annual extreme minimum winter temperature of −15 to −10 °F — the standard USDA measure of which perennials survive winter. 1 location in Arizona fall in this zone. It does not set planting dates; see the frost calendar below for that.

When should I plant tomatoes in Arizona's zone 5b?

Using Bellemont's frost dates (this page's median-season location): start seeds indoors about Apr 16 – Apr 30, then transplant outside about Jun 18 – Jun 25. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.

Does every location in Arizona's zone 5b have the same frost dates?

No — they do not all share a weather station, so frost dates vary by a week or more across the 1 locations listed (see the table above for each location's own dates).

USDA zone 5b in Arizona

−15 to −10 °F avg. annual extreme minimum · 1 location in this group · NOAA 1991–2020 normals

USDA plant hardiness zone 5b covers 1 location across Arizona (average annual extreme minimum −15 to −10 °F): Bellemont, AZ. Average last spring frost across this group ranges June 11 and growing seasons run 99 days — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Arizona location's own frost dates; the printable planting calendar uses Bellemont, this group's median-season location.

USDA zone: 5b−15 to −10 °F
Last frost range: Jun 11avg, 32°F
First frost range: Sep 25avg, 32°F
Growing season range: 99days

Locations in this group

Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.

Own frost dates per location.
Location	Also covers	Nearest station	Last frost	First frost	Season (days)
Bellemont *	—	Ft Valley	Jun 11	Sep 25	99

* Bellemont is this group's median-season location — the calendar below is computed from its data.

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.

Planting calendar (Bellemont, representative)

Computed from Bellemont's average frost dates — the median-season location in this Arizonazone 5b group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).

Crop

JanFebMarAprMayJunJulAugSepOctNovDec

Tomato

Pepper

Cucumber

Summer squash / zucchini

Start indoors
Plant out
Fall sowing
First harvest

Planting windows for Bellemont (Arizona, zone 5b), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Apr 16 – Apr 30	Jun 18 – Jun 25	Aug 17 – Sep 6	—	matures comfortably
Pepper	Very tender	Apr 2 – Apr 16	Jun 25 – Jul 2	Aug 24 – Sep 23	—	matures, but with little margin
Cucumber	Tender	May 14 – May 21	Jun 18 – Jun 25	Aug 7 – Aug 27	—	matures comfortably
Summer squash / zucchini	Tender	—	Jun 18 – Jun 25	Aug 2 – Aug 17	—	matures comfortably
Bush bean	Tender	—	Jun 18 – Jun 25	Aug 7 – Aug 17	Jul 27 – Aug 6	matures comfortably
Sweet corn	Tender	—	Jun 11 – Jun 25	Aug 10 – Sep 9	—	matures comfortably
Basil	Very tender	Apr 30 – May 14	Jun 18 – Jun 25	Jul 18 – Aug 2	—	matures comfortably
Lettuce	Half-hardy	Apr 30 – May 14	May 14 – May 28	Jun 28 – Jul 13	Jul 13 – Jul 28	matures comfortably
Pea	Hardy	—	Apr 30 – May 14	Jun 24 – Jul 9	Jul 3 – Jul 18	matures comfortably
Spinach	Hardy	—	Apr 30 – May 14	Jun 9 – Jun 19	Jul 23 – Aug 2	matures comfortably
Carrot	Half-hardy	—	May 21 – May 28	Jul 20 – Aug 9	Jun 23 – Jul 13	matures comfortably
Broccoli	Half-hardy	Apr 16 – Apr 30	May 14 – May 28	Jul 8 – Jul 28	Jun 28 – Jul 18	matures comfortably

Which crops fit this growing season

Using Bellemont's own 99-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 11 of 12 crops mature here with comfortable margin, 1matures with little room to spare. The tightest fits: pepper (+2 day margin). A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.

Frost & freeze dates (Bellemont)

From NOAA's 1991–2020 Climate Normals at station USC00023160. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.

Freeze probabilities by temperature threshold (MM/DD, NOAA 1991–2020), Bellemont.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	—	—	—	—	76
32°F (freeze)	Jun 11	Jun 30	Sep 25	Oct 6	99
28°F	May 27	Jun 14	Oct 4	Oct 19	129
24°F	May 5	May 27	Oct 14	Nov 1	159

Growing degree days

Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 1 locations is 1,730; Bellemont's own reading is shown below.

Annual growing degree days for Bellemont (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	1,730	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	3,739	cool-season crops (brassicas, greens)

Hardiness zone 5b in Arizona

Zone 5b means an average annual extreme minimum winter temperature of about −15 to −10 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Arizona spans 10 hardiness zones in this dataset — see all Arizona locations for the full range, including zones6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b, 10a.

Explore zone 5b in other states at zone 5b, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 5b mean in Arizona?: Zone 5b means an average annual extreme minimum winter temperature of −15 to −10 °F — the standard USDA measure of which perennials survive winter. 1 location in Arizona fall in this zone. It does not set planting dates; see the frost calendar below for that.
When should I plant tomatoes in Arizona's zone 5b?: Using Bellemont's frost dates (this page's median-season location): start seeds indoors about Apr 16 – Apr 30, then transplant outside about Jun 18 – Jun 25. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
Does every location in Arizona's zone 5b have the same frost dates?: No — they do not all share a weather station, so frost dates vary by a week or more across the 1 locations listed (see the table above for each location's own dates).

Sources & method

Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.