Palo Alto, CA 94027 planting calendar
- USDA zone
- 9b25 to 30 °F
- Last frost
- Jan 17avg, 32°F
- First frost
- Dec 12avg, 32°F
- Growing season
- 333days
Palo Alto, California is in USDA plant hardiness zone 9b. Its average last spring frost is around January 17 and the first fall frost around December 12, giving a growing season of about 333 days (NOAA 1991–2020 normals, 32°F, median). Start tender crops like tomatoes and peppers indoors weeks before the last frost and set them out afterward; sow hardy crops such as peas, spinach, and lettuce before it. The planner below turns those frost dates into a printable per-crop planting calendar.
Palo Alto planting calendar
Each crop's windows are counted from Palo Alto's average frost dates. 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.
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting |
|---|---|---|---|---|---|
| Tomato | Tender | Jan 1 | Jan 24 – Jan 31 | Mar 25 – Apr 14 | — |
| Pepper | Very tender | Jan 1 | Jan 31 – Feb 7 | Apr 1 – May 1 | — |
| Cucumber | Tender | Jan 1 | Jan 24 – Jan 31 | Mar 15 – Apr 4 | — |
| Summer squash / zucchini | Tender | — | Jan 24 – Jan 31 | Mar 10 – Mar 25 | — |
| Bush bean | Tender | — | Jan 24 – Jan 31 | Mar 15 – Mar 25 | Oct 13 – Oct 23 |
| Sweet corn | Tender | — | Jan 17 – Jan 31 | Mar 18 – Apr 17 | — |
| Basil | Very tender | Jan 1 | Jan 24 – Jan 31 | Feb 23 – Mar 10 | — |
| Lettuce | Half-hardy | Jan 1 | Jan 1 – Jan 3 | Feb 15 – Mar 2 | Sep 29 – Oct 14 |
| Pea | Hardy | — | Jan 1 | Feb 25 – Mar 12 | Sep 19 – Oct 4 |
| Spinach | Hardy | — | Jan 1 | Feb 10 – Feb 20 | Oct 9 – Oct 19 |
| Carrot | Half-hardy | — | Jan 1 – Jan 3 | Mar 2 – Mar 22 | Sep 9 – Sep 29 |
| Broccoli | Half-hardy | Jan 1 | Jan 1 – Jan 3 | Feb 25 – Mar 17 | Sep 14 – Oct 4 |
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.
Frost & freeze dates
From NOAA's 1991–2020 Climate Normals at station USC00047339. 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 (p10 for spring, p90 for fall) — 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 25 | Mar 31 | Nov 25 | Dec 14 | 272 |
| 32°F (freeze) | Jan 17 | Feb 16 | Dec 12 | Jan 14 | 333 |
| 28°F | Dec 31 | Jan 22 | Dec 26 | Jan 15 | 365 |
| 24°F | — | — | — | — | 365 |
32°F is the standard "freeze" line that damages tender crops; lighter 36°F frost can nip the most cold-sensitive plants, while hardy crops shrug off light frost down toward 28°F. Use the threshold that matches what you are protecting.
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. Warm-season crops need a long, warm GDD total; a short, cool GDD total favors greens and brassicas.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 3,606 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 7,084 | cool-season crops (brassicas, greens) |
Hardiness zone 9b
Palo Alto sits in USDA plant hardiness zone 9b on the 2023 map — meaning its average annual extreme minimum winter temperature is about 25 to 30 °F. That number 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.
Explore more places in zone 9b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Palo Alto?
- Palo Alto, California is in USDA plant hardiness zone 9b on the 2023 map (average annual extreme minimum temperature 25 to 30 °F) — from the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. See the methodology page for sources.
- When is the last frost in Palo Alto?
- The average (median) last spring frost at 32°F is around January 17, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as February 16, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Palo Alto?
- The average first fall frost at 32°F is around December 12. That leaves a growing season of about 333 days between the average last spring and first fall frosts.
- When should I start tomatoes in Palo Alto?
- Start tomato seeds indoors about Jan 1 and transplant them outside about Jan 24 – Jan 31, once the danger of frost has passed. Estimated first harvest is around Mar 25 – Apr 14.
- How long is the growing season in Palo Alto?
- About 333 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~January 17) and the average first fall frost (~December 12). Cold-hardy crops extend usable time at both ends; frost-tender crops fit inside it.
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020 for station USC00047339 (Redwood City, 4 km away). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to this 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.