USDA zone 9b in Arizona
USDA plant hardiness zone 9b covers 43 locations across Arizona (average annual extreme minimum 25 to 30 °F): Ali Chuk, AZ, Apache Junction, AZ, Aztec, AZ, Casa Blanca, AZ, Casas Adobes, AZ, Cave Creek, AZ, and 37 more. Average last spring frost across this group ranges January 4 (Fort Mohave) to April 2 (Marana), and growing seasons run 222–358 days (Marana to White Hills) — 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 Ehrenberg, this group's median-season location.
- USDA zone
- 9b25 to 30 °F
- Last frost range
- Jan 4–Apr 2avg, 32°F
- First frost range
- Nov 11–Dec 29avg, 32°F
- Growing season range
- 222–358days
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) |
|---|---|---|---|---|---|
| Ali Chuk | — | Organ Pipe Cactus Nm | Feb 4 | Dec 15 | 314 |
| Apache Junction | Gold Canyon | Apache Junction 5 Ne | Feb 11 | Dec 10 | 304 |
| Aztec | — | Dateland Whitewing Rch | Jan 25 | Dec 13 | 324 |
| Casa Blanca | — | Maricopa 4 N | Feb 23 | Nov 24 | 274 |
| Casas Adobes | — | Tohono Chul | Feb 26 | Dec 4 | 279 |
| Cave Creek | Carefree | Carefree | Feb 4 | Dec 16 | 313 |
| Charco | — | Ajo | Jan 10 | Dec 21 | 347 |
| Ehrenberg * | — | Quartzsite | Jan 28 | Dec 6 | 315 |
| Fort Mohave | Laughlin | Bullhead City | Jan 4 | Dec 23 | 356 |
| Fountain Hills | Rio Verde | Fountain Hills | Jan 6 | Dec 28 | 356 |
| Goodyear | Arlington, Theba | Gila Bend 2se | Jan 23 | Dec 11 | 323 |
| Jakes Corner | — | Punkin Ctr | Mar 7 | Nov 20 | 255 |
| Katherine | — | Laughlin | Jan 5 | Dec 24 | 354 |
| Marana | — | Catalina Sp | Apr 2 | Nov 11 | 222 |
| Marana | Picture Rocks, Avra Valley | Tucson 17 Nw | Feb 23 | Dec 6 | 287 |
| Mesa | San Tan Valley, Gilbert, Chandler, Queen Creek, Sun Lakes | Chandler Heights | Feb 1 | Dec 11 | 315 |
| Mesa | Queen Creek | E Mesa | Feb 1 | Dec 10 | 312 |
| Mohave Valley | Topock | Needles Ap | frost-free | frost-free | 365 |
| Oatman | — | Yucca 1 Nne | Feb 18 | Dec 2 | 288 |
| Parker | — | Bouse | Feb 18 | Nov 28 | 284 |
| Peoria | New River, Morristown | Castle Hot Springs | Jan 15 | Dec 22 | 341 |
| Phoenix | — | Phoenix Sky Harbor Intl Ap | frost-free | frost-free | 365 |
| Phoenix | Anthem | Phoenix Deer Valley Muni Ap | Jan 8 | Dec 25 | 354 |
| Phoenix | — | South Phoenix | Jan 21 | Dec 16 | 331 |
| Phoenix | Mesa, Chandler, Tempe, Paradise Valley | Tempe Asu | Feb 13 | Dec 5 | 298 |
| Phoenix | Buckeye, Avondale, Tolleson, Citrus Park, Litchfield Park | Litchfield Park | Jan 7 | Dec 24 | 351 |
| Phoenix | Santa Cruz, Guadalupe | Laveen 3 Sse | Jan 14 | Dec 22 | 343 |
| Phoenix | Surprise, Sun City West, El Mirage | Youngtown | Jan 20 | Dec 15 | 331 |
| Poston | — | Iron Mtn | frost-free | frost-free | 365 |
| Roosevelt | — | Roosevelt 1 S | Jan 17 | Dec 25 | 342 |
| San Tan Valley | Cactus Forest | Casa Grande Nm | Feb 17 | Nov 29 | 284 |
| Superior | Kearny | Superior | Jan 18 | Dec 28 | 342 |
| Surprise | Circle | Wittmann 1se | Feb 5 | Dec 11 | 306 |
| Tonopah | — | Painted Rock Dam | Jan 21 | Dec 15 | 327 |
| Tucson | South Tucson | Tucson Intl Ap | Feb 5 | Dec 9 | 307 |
| Tucson | — | Saguaro Np | Jan 26 | Dec 16 | 326 |
| Tucson | — | Tucson Wfo | Jan 20 | Dec 17 | 332 |
| Tucson | Flowing Wells | Tucson Camp Ave Exp | Feb 20 | Nov 27 | 280 |
| Tucson | Tucson Mountains | Tucson U Of A #1 | Feb 11 | Dec 2 | 293 |
| Wellton | Tacna | Tacna 3 Ne | Feb 13 | Dec 1 | 288 |
| White Hills | — | Temple Bar | Feb 4 | Dec 10 | 309 |
| White Hills | — | Willow Beach | Jan 7 | Dec 29 | 358 |
| Wikieup | — | Wikieup | Mar 19 | Nov 23 | 246 |
* Ehrenberg 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 (Ehrenberg, representative)
Computed from Ehrenberg's average frost dates — the median-season location in this Arizonazone 9b 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 | Feb 4 – Feb 11 | Apr 5 – Apr 25 | — | matures comfortably |
| Pepper | Very tender | Jan 1 | Feb 11 – Feb 18 | Apr 12 – May 12 | — | matures comfortably |
| Cucumber | Tender | Jan 1 – Jan 7 | Feb 4 – Feb 11 | Mar 26 – Apr 15 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Feb 4 – Feb 11 | Mar 21 – Apr 5 | — | matures comfortably |
| Bush bean | Tender | — | Feb 4 – Feb 11 | Mar 26 – Apr 5 | Oct 7 – Oct 17 | matures comfortably |
| Sweet corn | Tender | — | Jan 28 – Feb 11 | Mar 29 – Apr 28 | — | matures comfortably |
| Basil | Very tender | Jan 1 | Feb 4 – Feb 11 | Mar 6 – Mar 21 | — | matures comfortably |
| Lettuce | Half-hardy | Jan 1 | Jan 1 – Jan 14 | Feb 15 – Mar 2 | Sep 23 – Oct 8 | matures comfortably |
| Pea | Hardy | — | Jan 1 | Feb 25 – Mar 12 | Sep 13 – Sep 28 | matures comfortably |
| Spinach | Hardy | — | Jan 1 | Feb 10 – Feb 20 | Oct 3 – Oct 13 | matures comfortably |
| Carrot | Half-hardy | — | Jan 7 – Jan 14 | Mar 8 – Mar 28 | Sep 3 – Sep 23 | matures comfortably |
| Broccoli | Half-hardy | Jan 1 | Jan 1 – Jan 14 | Feb 25 – Mar 17 | Sep 8 – Sep 28 | matures comfortably |
Which crops fit this growing season
Using Ehrenberg's own 315-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 (Ehrenberg)
From NOAA's 1991–2020 Climate Normals at station USC00026865. 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 | Feb 17 | Mar 7 | Nov 27 | Dec 12 | 282 |
| 32°F (freeze) | Jan 28 | Feb 24 | Dec 6 | Dec 26 | 315 |
| 28°F | Jan 7 | Feb 5 | Dec 21 | Jan 13 | 349 |
| 24°F | Jan 2 | Jan 22 | Jan 1 | Jan 19 | 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 43 locations is 8,091; Ehrenberg's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 8,760 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 12,323 | cool-season crops (brassicas, greens) |
Hardiness zone 9b in Arizona
Zone 9b means an average annual extreme minimum winter temperature of about 25 to 30 °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, 10a.
Explore zone 9b in other states at zone 9b, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 9b mean in Arizona?
- Zone 9b means an average annual extreme minimum winter temperature of 25 to 30 °F — the standard USDA measure of which perennials survive winter. 43 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 9b is the growing season longest?
- White Hills runs the longest season on this page at about 358 days; Marana is shortest at about 222 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 9b?
- Using Ehrenberg's frost dates (this page's median-season location): start seeds indoors about Jan 1, then transplant outside about Feb 4 – Feb 11. 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 9b 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 43 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.