USDA zone 8a in Arizona
USDA plant hardiness zone 8a covers 19 locations across Arizona (average annual extreme minimum 10 to 15 °F): Antares, AZ, Chino Valley, AZ, Dewey-Humboldt, AZ, Dewey-Humboldt, AZ, Douglas, AZ, Duncan, AZ, and 13 more. Average last spring frost across this group ranges February 24 (Top-of-the-World) to May 24 (Paulden), and growing seasons run 135–279 days (Paulden to Top-of-the-World) — 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 Douglas, this group's median-season location.
- USDA zone
- 8a10 to 15 °F
- Last frost range
- Feb 24–May 24avg, 32°F
- First frost range
- Oct 7–Dec 1avg, 32°F
- Growing season range
- 135–279days
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) |
|---|---|---|---|---|---|
| Antares | — | Kingman Mohave Co Ap | Apr 2 | Nov 11 | 220 |
| Chino Valley | Prescott Valley | Prescott Love Fld | Apr 20 | Oct 27 | 188 |
| Dewey-Humboldt | — | Jerome | Mar 26 | Nov 25 | 242 |
| Dewey-Humboldt | Wilhoit | Prescott | Apr 30 | Oct 20 | 172 |
| Douglas * | — | Douglas Bisbee Inl Ap | Apr 11 | Nov 2 | 203 |
| Duncan | — | Duncan | Apr 24 | Oct 25 | 183 |
| Elgin | — | Elgin 5 S | Apr 18 | Nov 1 | 195 |
| Lake Montezuma | — | Montezuma Castle Nm | Apr 16 | Oct 30 | 196 |
| Morenci | — | Clifton | Feb 26 | Nov 23 | 268 |
| Patagonia | — | Nogales Intl Ap | Mar 20 | Nov 17 | 239 |
| Paulden | — | Walnut Creek | May 24 | Oct 7 | 135 |
| Pine | — | Natural Brg | Apr 9 | Nov 10 | 211 |
| Pirtleville | — | Douglas | Mar 18 | Nov 13 | 235 |
| Sonoita | — | Sonoita | Mar 28 | Nov 21 | 237 |
| Spring Valley | — | Cordes | Apr 5 | Nov 17 | 221 |
| Sunizona | — | Pearce - Sunsites | Apr 14 | Nov 2 | 200 |
| Top-of-the-World | — | Miami | Feb 24 | Dec 1 | 279 |
| Truxton | Crozier | Diamond M Rch | May 17 | Oct 10 | 146 |
| Young | — | Pleasant Valley | May 6 | Oct 20 | 165 |
* Douglas 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 (Douglas, representative)
Computed from Douglas's average frost dates — the median-season location in this Arizonazone 8a 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 | Feb 14 – Feb 28 | Apr 18 – Apr 25 | Jun 17 – Jul 7 | — | matures comfortably |
| Pepper | Very tender | Jan 31 – Feb 14 | Apr 25 – May 2 | Jun 24 – Jul 24 | — | matures comfortably |
| Cucumber | Tender | Mar 14 – Mar 21 | Apr 18 – Apr 25 | Jun 7 – Jun 27 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Apr 18 – Apr 25 | Jun 2 – Jun 17 | — | matures comfortably |
| Bush bean | Tender | — | Apr 18 – Apr 25 | Jun 7 – Jun 17 | Sep 3 – Sep 13 | matures comfortably |
| Sweet corn | Tender | — | Apr 11 – Apr 25 | Jun 10 – Jul 10 | — | matures comfortably |
| Basil | Very tender | Feb 28 – Mar 14 | Apr 18 – Apr 25 | May 18 – Jun 2 | — | matures comfortably |
| Lettuce | Half-hardy | Feb 28 – Mar 14 | Mar 14 – Mar 28 | Apr 28 – May 13 | Aug 20 – Sep 4 | matures comfortably |
| Pea | Hardy | — | Feb 28 – Mar 14 | Apr 24 – May 9 | Aug 10 – Aug 25 | matures comfortably |
| Spinach | Hardy | — | Feb 28 – Mar 14 | Apr 9 – Apr 19 | Aug 30 – Sep 9 | matures comfortably |
| Carrot | Half-hardy | — | Mar 21 – Mar 28 | May 20 – Jun 9 | Jul 31 – Aug 20 | matures comfortably |
| Broccoli | Half-hardy | Feb 14 – Feb 28 | Mar 14 – Mar 28 | May 8 – May 28 | Aug 5 – Aug 25 | matures comfortably |
Which crops fit this growing season
Using Douglas's own 203-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 (Douglas)
From NOAA's 1991–2020 Climate Normals at station USW00093026. 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 | Apr 25 | May 8 | Oct 25 | Nov 6 | 182 |
| 32°F (freeze) | Apr 11 | Apr 27 | Nov 2 | Nov 15 | 203 |
| 28°F | Mar 27 | Apr 15 | Nov 12 | Nov 26 | 227 |
| 24°F | Mar 5 | Mar 31 | Nov 22 | Dec 7 | 257 |
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 19 locations is 4,797; Douglas's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 5,020 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 8,209 | cool-season crops (brassicas, greens) |
Hardiness zone 8a in Arizona
Zone 8a means an average annual extreme minimum winter temperature of about 10 to 15 °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, 8b, 9a, 9b, 10a.
Explore zone 8a in other states at zone 8a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 8a mean in Arizona?
- Zone 8a means an average annual extreme minimum winter temperature of 10 to 15 °F — the standard USDA measure of which perennials survive winter. 19 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 8a is the growing season longest?
- Top-of-the-World runs the longest season on this page at about 279 days; Paulden is shortest at about 135 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 8a?
- Using Douglas's frost dates (this page's median-season location): start seeds indoors about Feb 14 – Feb 28, then transplant outside about Apr 18 – Apr 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 8a 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 19 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.