USDA zone 9a in Arizona
USDA plant hardiness zone 9a covers 31 locations across Arizona (average annual extreme minimum 20 to 25 °F): Aguila, AZ, Bagdad, AZ, Black Canyon, AZ, Casa Grande, AZ, Casas Adobes, AZ, Catalina Foothills, AZ, and 25 more. Average last spring frost across this group ranges January 4 (Golden Valley) to April 26 (South Komelik), and growing seasons run 195–356 days (South Komelik to Golden Valley) — 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 Casas Adobes, this group's median-season location.
- USDA zone
- 9a20 to 25 °F
- Last frost range
- Jan 4–Apr 26avg, 32°F
- First frost range
- Nov 4–Dec 24avg, 32°F
- Growing season range
- 195–356days
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) |
|---|---|---|---|---|---|
| Aguila | — | Aguila | Mar 17 | Nov 19 | 243 |
| Bagdad | — | Bagdad | Apr 7 | Nov 12 | 217 |
| Black Canyon | — | Cordes | Apr 5 | Nov 17 | 221 |
| Casa Grande | Chuichu | Casa Grande | Feb 5 | Dec 6 | 305 |
| Casas Adobes * | — | Tohono Chul | Feb 26 | Dec 4 | 279 |
| Catalina Foothills | — | Tucson Camp Ave Exp | Feb 20 | Nov 27 | 280 |
| Congress | Wickenburg | Wickenburg | Mar 7 | Nov 20 | 254 |
| Coolidge | Upper Santan | Casa Grande Nm | Feb 17 | Nov 29 | 284 |
| Dolan Springs | — | Laughlin | Jan 5 | Dec 24 | 354 |
| Eloy | — | Arizona City | Feb 28 | Nov 21 | 266 |
| Eloy | Red Rock, Picacho | Picacho 8 Se | Feb 6 | Dec 9 | 308 |
| Golden Valley | — | Bullhead City | Jan 4 | Dec 23 | 356 |
| Maricopa | Ak-Chin, Stanfield | Maricopa 4 N | Feb 23 | Nov 24 | 274 |
| Martinez Lake | — | Kofa Mine | frost-free | frost-free | 365 |
| Meadview | — | Meadview 1w | Mar 5 | Nov 28 | 265 |
| Oracle | Dudleyville | Oracle Sp | Mar 29 | Nov 13 | 225 |
| Peridot | Hayden, Winkelman | San Carlos Reservoir | Mar 13 | Nov 19 | 247 |
| Quartzsite | — | Quartzsite | Jan 28 | Dec 6 | 315 |
| Saddlebrooke | Oro Valley | Catalina Sp | Apr 2 | Nov 11 | 222 |
| Sahuarita | Elephant Head, Arivaca Junction | Green Valley | Feb 25 | Nov 27 | 276 |
| Salome | Utting, Poston | Bouse | Feb 18 | Nov 28 | 284 |
| San Carlos | Wheatfields, Claypool | Miami | Feb 24 | Dec 1 | 279 |
| San Manuel | — | San Manuel | Feb 4 | Dec 8 | 306 |
| South Komelik | Nolic | Kitt Peak | Apr 26 | Nov 4 | 195 |
| Three Points | — | Anvil Rch | Mar 27 | Nov 9 | 226 |
| Tonto Basin | — | Punkin Ctr | Mar 7 | Nov 20 | 255 |
| Tucson | Tanque Verde, Vail | Saguaro Np | Jan 26 | Dec 16 | 326 |
| Tucson | Valencia West | Tucson Intl Ap | Feb 5 | Dec 9 | 307 |
| Valencia West | — | Tucson 17 Nw | Feb 23 | Dec 6 | 287 |
| Wenden | — | Alamo Dam | Mar 4 | Nov 23 | 261 |
| Yucca | — | Yucca 1 Nne | Feb 18 | Dec 2 | 288 |
* Casas Adobes 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 (Casas Adobes, representative)
Computed from Casas Adobes's average frost dates — the median-season location in this Arizonazone 9a 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 15 | Mar 5 – Mar 12 | May 4 – May 24 | — | matures comfortably |
| Pepper | Very tender | Jan 1 | Mar 12 – Mar 19 | May 11 – Jun 10 | — | matures comfortably |
| Cucumber | Tender | Jan 29 – Feb 5 | Mar 5 – Mar 12 | Apr 24 – May 14 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Mar 5 – Mar 12 | Apr 19 – May 4 | — | matures comfortably |
| Bush bean | Tender | — | Mar 5 – Mar 12 | Apr 24 – May 4 | Oct 5 – Oct 15 | matures comfortably |
| Sweet corn | Tender | — | Feb 26 – Mar 12 | Apr 27 – May 27 | — | matures comfortably |
| Basil | Very tender | Jan 15 – Jan 29 | Mar 5 – Mar 12 | Apr 4 – Apr 19 | — | matures comfortably |
| Lettuce | Half-hardy | Jan 15 – Jan 29 | Jan 29 – Feb 12 | Mar 15 – Mar 30 | Sep 21 – Oct 6 | matures comfortably |
| Pea | Hardy | — | Jan 15 – Jan 29 | Mar 11 – Mar 26 | Sep 11 – Sep 26 | matures comfortably |
| Spinach | Hardy | — | Jan 15 – Jan 29 | Feb 24 – Mar 6 | Oct 1 – Oct 11 | matures comfortably |
| Carrot | Half-hardy | — | Feb 5 – Feb 12 | Apr 6 – Apr 26 | Sep 1 – Sep 21 | matures comfortably |
| Broccoli | Half-hardy | Jan 1 – Jan 15 | Jan 29 – Feb 12 | Mar 25 – Apr 14 | Sep 6 – Sep 26 | matures comfortably |
Which crops fit this growing season
Using Casas Adobes's own 279-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 (Casas Adobes)
From NOAA's 1991–2020 Climate Normals at station USC00028590. 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 | Mar 17 | Apr 9 | Nov 21 | Dec 6 | 245 |
| 32°F (freeze) | Feb 26 | Mar 18 | Dec 4 | Dec 19 | 279 |
| 28°F | Feb 1 | Feb 27 | Dec 17 | Jan 16 | 320 |
| 24°F | Jan 13 | Feb 14 | Jan 2 | Feb 5 | 361 |
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 31 locations is 7,171; Casas Adobes's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 7,240 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 10,740 | cool-season crops (brassicas, greens) |
Hardiness zone 9a in Arizona
Zone 9a means an average annual extreme minimum winter temperature of about 20 to 25 °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, 9b, 10a.
Explore zone 9a in other states at zone 9a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 9a mean in Arizona?
- Zone 9a means an average annual extreme minimum winter temperature of 20 to 25 °F — the standard USDA measure of which perennials survive winter. 31 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 9a is the growing season longest?
- Golden Valley runs the longest season on this page at about 356 days; South Komelik is shortest at about 195 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 9a?
- Using Casas Adobes's frost dates (this page's median-season location): start seeds indoors about Jan 1 – Jan 15, then transplant outside about Mar 5 – Mar 12. 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 9a 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 31 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.