USDA zone 10a in Arizona
USDA plant hardiness zone 10a covers 14 locations across Arizona (average annual extreme minimum 30 to 35 °F): Bullhead, AZ, Cibola, AZ, Fortuna Foothills, AZ, Lake Havasu, AZ, Parker Strip, AZ, Phoenix, AZ, and 8 more. Average last spring frost across this group ranges January 4 (Bullhead) to February 13 (Tempe), and growing seasons run 298–361 days (Tempe to Fortuna Foothills) — 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 Phoenix, this group's median-season location.
- USDA zone
- 10a30 to 35 °F
- Last frost range
- Jan 4–Feb 13avg, 32°F
- First frost range
- Dec 5–Dec 28avg, 32°F
- Growing season range
- 298–361days
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.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Bullhead | — | Bullhead City | Jan 4 | Dec 23 | 356 |
| Cibola | — | Blythe Ap | Jan 5 | Dec 21 | 347 |
| Fortuna Foothills | Buckshot | Yuma Proving Ground | Jan 4 | Dec 25 | 361 |
| Lake Havasu | Crystal Beach | Lake Havasu City | frost-free | frost-free | 365 |
| Parker Strip | — | Parker Resrvoir | frost-free | frost-free | 365 |
| Phoenix | — | Phoenix Deer Valley Muni Ap | Jan 8 | Dec 25 | 354 |
| Phoenix | Guadalupe | Phoenix Sky Harbor Intl Ap | frost-free | frost-free | 365 |
| Phoenix | Komatke, Guadalupe | Laveen 3 Sse | Jan 14 | Dec 22 | 343 |
| Phoenix * | — | Scottsdale Muni Ap | Jan 6 | Dec 26 | 353 |
| San Luis | Somerton, Avenue B and C, Winterhaven | Yuma Mcas | frost-free | frost-free | 365 |
| Scottsdale | — | Fountain Hills | Jan 6 | Dec 28 | 356 |
| Scottsdale | — | Carefree | Feb 4 | Dec 16 | 313 |
| Tempe | — | Tempe Asu | Feb 13 | Dec 5 | 298 |
| Topock | — | Needles Ap | frost-free | frost-free | 365 |
* Phoenix 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 (Phoenix, representative)
Computed from Phoenix's average frost dates — the median-season location in this Arizonazone 10a 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).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Jan 1 | Jan 13 – Jan 20 | Mar 14 – Apr 3 | — | matures comfortably |
| Pepper | Very tender | Jan 1 | Jan 20 – Jan 27 | Mar 21 – Apr 20 | — | matures comfortably |
| Cucumber | Tender | Jan 1 | Jan 13 – Jan 20 | Mar 4 – Mar 24 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Jan 13 – Jan 20 | Feb 27 – Mar 14 | — | matures comfortably |
| Bush bean | Tender | — | Jan 13 – Jan 20 | Mar 4 – Mar 14 | Oct 27 – Nov 6 | matures comfortably |
| Sweet corn | Tender | — | Jan 6 – Jan 20 | Mar 7 – Apr 6 | — | matures comfortably |
| Basil | Very tender | Jan 1 | Jan 13 – Jan 20 | Feb 12 – Feb 27 | — | matures comfortably |
| Lettuce | Half-hardy | Jan 1 | Jan 1 | Feb 15 – Mar 2 | Oct 13 – Oct 28 | matures comfortably |
| Pea | Hardy | — | Jan 1 | Feb 25 – Mar 12 | Oct 3 – Oct 18 | matures comfortably |
| Spinach | Hardy | — | Jan 1 | Feb 10 – Feb 20 | Oct 23 – Nov 2 | matures comfortably |
| Carrot | Half-hardy | — | Jan 1 | Mar 2 – Mar 22 | Sep 23 – Oct 13 | matures comfortably |
| Broccoli | Half-hardy | Jan 1 | Jan 1 | Feb 25 – Mar 17 | Sep 28 – Oct 18 | matures comfortably |
Which crops fit this growing season
Using Phoenix's own 353-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable 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 (Phoenix)
From NOAA's 1991–2020 Climate Normals at station USW00003192. 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.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | Jan 30 | Feb 26 | Dec 11 | Dec 30 | 316 |
| 32°F (freeze) | Jan 6 | Feb 7 | Dec 26 | Jan 20 | 353 |
| 28°F | Jan 2 | Jan 20 | Jan 1 | Jan 17 | 365 |
| 24°F | — | — | — | — | 365 |
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 14 locations is 8,904; Phoenix's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 8,567 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 12,157 | cool-season crops (brassicas, greens) |
Hardiness zone 10a in Arizona
Zone 10a means an average annual extreme minimum winter temperature of about 30 to 35 °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 zones5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b.
Explore zone 10a in other states at zone 10a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 10a mean in Arizona?
- Zone 10a means an average annual extreme minimum winter temperature of 30 to 35 °F — the standard USDA measure of which perennials survive winter. 14 locations in Arizona fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in Arizona's zone 10a is the growing season longest?
- Fortuna Foothills runs the longest season on this page at about 361 days; Tempe is shortest at about 298 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in Arizona's zone 10a?
- Using Phoenix's frost dates (this page's median-season location): start seeds indoors about Jan 1, then transplant outside about Jan 13 – Jan 20. 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 10a 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 14 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.