USDA zone 8a in California
USDA plant hardiness zone 8a covers 22 locations across California (average annual extreme minimum 10 to 15 °F): Alta, CA, Castella, CA, Downieville, CA, Edwards AFB, CA, Etna, CA, Fish Camp, CA, and 16 more. Average last spring frost across this group ranges February 23 (Shaver Lake) to May 27 (Lake Arrowhead), and growing seasons run 122–294 days (Meadow Valley to Shaver Lake) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every California location's own frost dates; the printable planting calendar uses Downieville, this group's median-season location.
- USDA zone
- 8a10 to 15 °F
- Last frost range
- Feb 23–May 27avg, 32°F
- First frost range
- Sep 25–Dec 12avg, 32°F
- Growing season range
- 122–294days
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) |
|---|---|---|---|---|---|
| Alta | — | Blue Canyon Ap | May 4 | Nov 4 | 183 |
| Castella | — | Dunsmuir Trtmt Pl | Apr 23 | Oct 27 | 185 |
| Downieville * | — | Downieville | Apr 28 | Oct 25 | 178 |
| Edwards AFB | — | Palmdale Ap | Mar 18 | Nov 15 | 241 |
| Etna | — | Orleans | Mar 12 | Nov 26 | 262 |
| Fish Camp | — | So Entrance Yosemite Np | May 24 | Oct 10 | 137 |
| Gasquet | — | Cave Junction 1 Wnw | May 1 | Oct 12 | 161 |
| Greenview | Etna, Gazelle | Callahan | May 20 | Oct 5 | 135 |
| Idyllwild-Pine Cove | — | Idyllwild Fire Dept | May 16 | Oct 24 | 160 |
| La Porte | — | Strawberry Valley | May 4 | Oct 30 | 174 |
| Lake Arrowhead | Crestline | Lake Arrowhead | May 5 | Nov 2 | 176 |
| Lake Arrowhead | Running Springs | Big Bear Lake | May 27 | Oct 4 | 131 |
| Lake Shastina | Mount Shasta | Mt Shasta | May 6 | Oct 12 | 158 |
| Lancaster | — | Lancaster Wm J Fox Fld | Apr 3 | Nov 1 | 211 |
| Lone Pine | Independence | Independence | Mar 31 | Nov 9 | 224 |
| Long Barn | — | Cherry Valley Dam | May 2 | Nov 4 | 183 |
| Lytle Creek | Wrightwood | Wrightwood | May 16 | Oct 13 | 151 |
| Meadow Valley | — | Quincy | May 22 | Sep 25 | 122 |
| Pine Valley | — | Cuyamaca | Apr 19 | Oct 27 | 190 |
| Shaver Lake | — | Balch Pwr House | Feb 23 | Dec 12 | 294 |
| Wrightwood | — | Pearblossom | Mar 13 | Dec 1 | 258 |
| Yreka | Hornbrook, Fort Jones, Grenada | Yreka | Apr 30 | Oct 18 | 169 |
* Downieville 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 (Downieville, representative)
Computed from Downieville's average frost dates — the median-season location in this Californiazone 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 | Mar 3 – Mar 17 | May 5 – May 12 | Jul 4 – Jul 24 | — | matures comfortably |
| Pepper | Very tender | Feb 17 – Mar 3 | May 12 – May 19 | Jul 11 – Aug 10 | — | matures comfortably |
| Cucumber | Tender | Mar 31 – Apr 7 | May 5 – May 12 | Jun 24 – Jul 14 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 5 – May 12 | Jun 19 – Jul 4 | — | matures comfortably |
| Bush bean | Tender | — | May 5 – May 12 | Jun 24 – Jul 4 | Aug 26 – Sep 5 | matures comfortably |
| Sweet corn | Tender | — | Apr 28 – May 12 | Jun 27 – Jul 27 | — | matures comfortably |
| Basil | Very tender | Mar 17 – Mar 31 | May 5 – May 12 | Jun 4 – Jun 19 | — | matures comfortably |
| Lettuce | Half-hardy | Mar 17 – Mar 31 | Mar 31 – Apr 14 | May 15 – May 30 | Aug 12 – Aug 27 | matures comfortably |
| Pea | Hardy | — | Mar 17 – Mar 31 | May 11 – May 26 | Aug 2 – Aug 17 | matures comfortably |
| Spinach | Hardy | — | Mar 17 – Mar 31 | Apr 26 – May 6 | Aug 22 – Sep 1 | matures comfortably |
| Carrot | Half-hardy | — | Apr 7 – Apr 14 | Jun 6 – Jun 26 | Jul 23 – Aug 12 | matures comfortably |
| Broccoli | Half-hardy | Mar 3 – Mar 17 | Mar 31 – Apr 14 | May 25 – Jun 14 | Jul 28 – Aug 17 | matures comfortably |
Which crops fit this growing season
Using Downieville's own 178-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 (Downieville)
From NOAA's 1991–2020 Climate Normals at station USC00042500. 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 | May 24 | Jun 11 | Oct 8 | Oct 22 | 137 |
| 32°F (freeze) | Apr 28 | May 22 | Oct 25 | Nov 8 | 178 |
| 28°F | Apr 6 | Apr 25 | Nov 10 | Dec 1 | 219 |
| 24°F | Feb 20 | Mar 30 | Dec 1 | Dec 26 | 288 |
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 22 locations is 2,779; Downieville's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 2,642 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 5,106 | cool-season crops (brassicas, greens) |
Hardiness zone 8a in California
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. California spans 12 hardiness zones in this dataset — see all California locations for the full range, including zones5b, 6a, 6b, 7a, 7b, 8b, 9a, 9b, 10a, 10b, 11a.
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 California?
- Zone 8a means an average annual extreme minimum winter temperature of 10 to 15 °F — the standard USDA measure of which perennials survive winter. 22 locations in California fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in California's zone 8a is the growing season longest?
- Shaver Lake runs the longest season on this page at about 294 days; Meadow Valley is shortest at about 122 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 California's zone 8a?
- Using Downieville's frost dates (this page's median-season location): start seeds indoors about Mar 3 – Mar 17, then transplant outside about May 5 – May 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 California'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 22 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.