Frost Dates & Planting Calendar for Hillsborough, CA
Plan your garden around Hillsborough, CA's typical frost-free growing season, using NOAA climate normals and a 42-crop planting calendar built for this location.
Last Spring Frost
December 29
Safe Jan 13
Typical Dec 29
Risky Dec 11
First Fall Frost
December 26
Safe Dec 11
Typical Dec 26
Risky Jan 13
Growing Season
365 days
Typical last frost to typical first frost.
USDA Hardiness Zone
Zone 10a
Subtropical to frost-free — heat, not cold, is the main limit on what you can grow.
Data: NOAA station SAN FRANCISCO INTL AP, CA US, 5.2 km away.
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days until the typical last spring frost
Monthly Temperatures
Avg. high
Avg. temp
Avg. low
Planting Calendar
| Crop | Start indoors | Direct sow | Transplant | Fall planting | Maturity | Notes |
|---|---|---|---|---|---|---|
| Tomato | Nov 3 – Nov 17 | — | Jan 5 – Jan 12 | — | 60–85 days | Start indoors 6-8 weeks before last frost; transplant out 1-2 weeks after last frost once soil has warmed. |
| Pepper | Oct 20 – Nov 3 | — | Jan 5 – Jan 19 | — | 60–90 days | Slow to germinate; start indoors 8-10 weeks before last frost. Transplant only once nights stay above 55F, 1-3 weeks after last frost. |
| Eggplant | Oct 20 – Nov 3 | — | Jan 12 – Jan 19 | — | 65–85 days | Warm-season crop, similar timing to pepper; needs consistently warm soil (65F+) to transplant. |
| Cucumber | Dec 1 – Dec 8 | Jan 5 – Jan 12 | Jan 5 – Jan 12 | — | 50–65 days | Can be started indoors 3-4 weeks before transplanting, or direct-sown 1-2 weeks after last frost once soil is warm. |
| Zucchini | Dec 8 – Dec 15 | Jan 5 – Jan 19 | Jan 5 – Jan 12 | — | 45–55 days | Fast-growing squash; direct sow 1-3 weeks after last frost, or start indoors 2-3 weeks early for a head start. |
| Winter Squash | Dec 1 – Dec 8 | Jan 5 – Jan 19 | Jan 5 – Jan 12 | — | 80–110 days | Long season; direct sow after soil warms, or start indoors 3-4 weeks before last frost in short-season climates. |
| Pumpkin | — | Jan 5 – Jan 19 | — | — | 90–120 days | Direct sow 1-3 weeks after last frost; back-time from your first fall frost so the 90-120 day maturity window lands before it. |
| Watermelon | Dec 1 – Dec 8 | — | Jan 12 – Jan 19 | — | 70–90 days | Needs warm soil (65F+); start indoors 3-4 weeks before last frost, transplant 2-3 weeks after last frost. |
| Cantaloupe | Dec 1 – Dec 8 | — | Jan 12 – Jan 19 | — | 70–90 days | Same warm-soil requirements as watermelon; avoid disturbing roots when transplanting. |
| Corn | — | Dec 29 – Jan 12 | — | — | 60–100 days | Direct sow at last frost to 2 weeks after, once soil reaches 60F; does not transplant well. Succession sow every 2 weeks. |
| Green Bean | — | Dec 29 – Jan 12 | — | — | 50–65 days | Direct sow at last frost to 2 weeks after, once soil has warmed; frost-tender, do not rush. |
| Pea | — | Nov 17 – Dec 1 | — | — | 55–70 days | Cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Lettuce | — | Dec 1 – Dec 15 | — | Oct 31 – Nov 14 | 45–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. Also transplantable from indoor starts. |
| Spinach | — | Nov 17 – Dec 1 | — | Oct 31 – Nov 14 | 40–50 days | Very cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Kale | — | Dec 1 – Dec 15 | — | Oct 17 – Oct 31 | 50–65 days | Cold-hardy; direct sow 2-4 weeks before last frost or start indoors for earlier transplants. |
| Arugula | — | Dec 1 – Dec 15 | — | Nov 14 – Nov 21 | 30–40 days | Fast-growing, cold-tolerant green; direct sow 2-4 weeks before last frost, succession sow every 2-3 weeks. |
| Swiss Chard | — | Dec 8 – Dec 22 | — | — | 50–60 days | Fairly cold-hardy; direct sow 1-3 weeks before last frost. Tolerates light frost in fall too. |
| Broccoli | Nov 10 – Nov 24 | — | Dec 8 – Dec 15 | Oct 24 – Oct 31 | 55–80 days | Start indoors 5-7 weeks before last frost; transplant out 2-3 weeks before last frost (hardens off to light frost). |
| Cauliflower | Nov 10 – Nov 24 | — | Dec 15 – Dec 22 | Oct 17 – Oct 24 | 55–85 days | Fussier than broccoli about temperature swings; start indoors 5-7 weeks before last frost, transplant 1-2 weeks before last frost. |
| Cabbage | Nov 10 – Nov 24 | — | Dec 1 – Dec 15 | Oct 17 – Oct 31 | 60–100 days | Cold-hardy; start indoors 5-7 weeks before last frost, transplant 2-4 weeks before last frost. |
| Brussels Sprouts | Nov 10 – Nov 24 | — | Dec 8 – Dec 22 | — | 90–110 days | Long-season crop best timed to mature after a light fall frost for sweetest flavor; start indoors 5-7 weeks before last frost. |
| Carrot | — | Dec 1 – Dec 15 | — | Oct 3 – Oct 17 | 60–80 days | Direct sow only (does not transplant); sow 2-4 weeks before last frost, as soon as soil can be worked. |
| Beet | — | Dec 1 – Dec 15 | — | Oct 17 – Oct 31 | 50–65 days | Direct sow 2-4 weeks before last frost; tolerates light frost. |
| Radish | — | Nov 24 – Dec 8 | — | Nov 14 – Nov 28 | 22–30 days | Very fast and cold-hardy; direct sow 3-5 weeks before last frost, as soon as soil can be worked. |
| Turnip | — | Dec 1 – Dec 15 | — | Oct 17 – Oct 31 | 40–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. |
| Onion | Oct 20 – Nov 3 | — | Dec 1 – Dec 15 | — | 90–120 days | Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings. |
| Garlic | — | — | — | Nov 28 – Dec 12 | 240–270 days | Fall-planted crop only; not planted in spring in most climates. |
| Potato | — | Dec 1 – Dec 15 | — | — | 70–120 days | Plant seed potatoes 2-4 weeks before last frost, as soon as soil can be worked and is above 45F; light frost on emerging foliage is usually tolerated. |
| Sweet Potato | — | — | Jan 12 – Jan 26 | — | 90–120 days | Set out slips 2-4 weeks after last frost once soil is thoroughly warm (65F+); very frost/cold sensitive. |
| Asparagus | — | — | Dec 1 – Dec 15 | — | 730–1095 days | Perennial; plant crowns 2-4 weeks before last frost as soon as soil can be worked. Takes 2-3 years to full production. |
| Crop | Start indoors | Direct sow | Transplant | Fall planting | Maturity | Notes |
|---|---|---|---|---|---|---|
| Basil | Nov 17 – Nov 24 | — | Jan 5 – Jan 12 | — | 50–70 days | Very frost/cold sensitive; start indoors 5-6 weeks before last frost, transplant only after all danger of frost (1-2 weeks after) and nights stay warm. |
| Cilantro | — | Dec 8 – Dec 22 | — | Oct 31 – Nov 14 | 45–70 days | Cool-season, bolts in heat; direct sow 1-3 weeks before last frost, succession sow through spring. |
| Parsley | Nov 3 – Nov 17 | — | Dec 15 – Dec 22 | — | 70–90 days | Slow to germinate; start indoors 6-8 weeks before last frost, transplant 1-2 weeks before last frost (biennial, cold-tolerant). |
| Dill | — | Dec 8 – Dec 22 | — | — | 40–60 days | Taprooted, does not transplant well; direct sow 1-3 weeks before last frost, succession sow through summer. |
| Oregano | Nov 3 – Nov 17 | — | Dec 29 – Jan 5 | — | 80–90 days | Perennial herb; start indoors 6-8 weeks before last frost, transplant around/just after last frost date. |
| Thyme | Nov 3 – Nov 17 | — | Dec 29 – Jan 5 | — | 85–95 days | Perennial herb, slow from seed; start indoors 6-8 weeks before last frost, transplant around/after last frost. |
| Crop | Start indoors | Direct sow | Transplant | Fall planting | Maturity | Notes |
|---|---|---|---|---|---|---|
| Sunflower | — | Jan 5 – Jan 19 | — | — | 70–100 days | Direct sow 1-3 weeks after last frost once soil has warmed; taprooted, resents transplanting. |
| Zinnia | Dec 1 – Dec 8 | Jan 5 – Jan 19 | Jan 5 – Jan 12 | — | 60–70 days | Frost-tender; direct sow 1-3 weeks after last frost, or start indoors 3-4 weeks early for earlier blooms. |
| Marigold | Nov 17 – Dec 1 | — | Jan 5 – Jan 12 | — | 45–60 days | Frost-tender; start indoors 4-6 weeks before last frost, transplant after all frost danger has passed. |
| Cosmos | Dec 1 – Dec 8 | Jan 5 – Jan 19 | Jan 5 – Jan 12 | — | 60–90 days | Easy from direct seed 1-3 weeks after last frost; can also start indoors 3-4 weeks early. |
| Nasturtium | — | Jan 5 – Jan 19 | — | — | 50–65 days | Frost-tender, resents root disturbance; direct sow 1-3 weeks after last frost once soil has warmed. |
| Dahlia | — | — | Jan 5 – Jan 19 | — | 90–120 days | Plant tubers 1-3 weeks after last frost once soil is warm (60F+); very frost-sensitive. |
Date ranges are estimates based on university extension guidelines and this city's NOAA frost normals — not a guarantee. Scroll to see all columns on narrow screens.
Frequently Asked Questions
When is the last frost in Hillsborough, CA?
Based on 1991–2020 NOAA climate normals for the SAN FRANCISCO INTL AP, CA US station, the last spring frost in Hillsborough typically falls around December 29. A cautious gardener might wait until January 13 (only a 10% chance of a later frost), while December 11 marks an earlier, higher-risk planting date.
When is the first frost in Hillsborough, CA in fall?
The first fall frost in Hillsborough typically arrives around December 26. To stay safe, assume frost could start as early as December 11; in milder years it can hold off until January 13.
How long is the growing season in Hillsborough, CA?
Hillsborough's average frost-free growing season is about 365 days, running from the typical last spring frost (December 29) to the typical first fall frost (December 26).
What USDA hardiness zone is Hillsborough, CA in?
Hillsborough, CA is in USDA plant hardiness zone 10a, per the USDA's 2023 Plant Hardiness Zone Map. Subtropical to frost-free — heat, not cold, is the main limit on what you can grow.