Frost Dates & Planting Calendar for Union City, CA
Plan your garden around Union City, CA's typical frost-free growing season, using NOAA climate normals and a 42-crop planting calendar built for this location.
Last Spring Frost
January 7
Safe Feb 7
Typical Jan 7
Risky Dec 14
First Fall Frost
December 22
Safe Dec 2
Typical Dec 22
Risky Jan 21
Growing Season
353 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 FREMONT, CA US, 6 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 12 – Nov 26 | — | Jan 14 – Jan 21 | — | 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 29 – Nov 12 | — | Jan 14 – Jan 28 | — | 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 29 – Nov 12 | — | Jan 21 – Jan 28 | — | 65–85 days | Warm-season crop, similar timing to pepper; needs consistently warm soil (65F+) to transplant. |
| Cucumber | Dec 10 – Dec 17 | Jan 14 – Jan 21 | Jan 14 – Jan 21 | — | 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 17 – Dec 24 | Jan 14 – Jan 28 | Jan 14 – Jan 21 | — | 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 10 – Dec 17 | Jan 14 – Jan 28 | Jan 14 – Jan 21 | — | 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 14 – Jan 28 | — | — | 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 10 – Dec 17 | — | Jan 21 – Jan 28 | — | 70–90 days | Needs warm soil (65F+); start indoors 3-4 weeks before last frost, transplant 2-3 weeks after last frost. |
| Cantaloupe | Dec 10 – Dec 17 | — | Jan 21 – Jan 28 | — | 70–90 days | Same warm-soil requirements as watermelon; avoid disturbing roots when transplanting. |
| Corn | — | Jan 7 – Jan 21 | — | — | 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 | — | Jan 7 – Jan 21 | — | — | 50–65 days | Direct sow at last frost to 2 weeks after, once soil has warmed; frost-tender, do not rush. |
| Pea | — | Nov 26 – Dec 10 | — | — | 55–70 days | Cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Lettuce | — | Dec 10 – Dec 24 | — | Oct 27 – Nov 10 | 45–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. Also transplantable from indoor starts. |
| Spinach | — | Nov 26 – Dec 10 | — | Oct 27 – Nov 10 | 40–50 days | Very cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Kale | — | Dec 10 – Dec 24 | — | Oct 13 – Oct 27 | 50–65 days | Cold-hardy; direct sow 2-4 weeks before last frost or start indoors for earlier transplants. |
| Arugula | — | Dec 10 – Dec 24 | — | Nov 10 – Nov 17 | 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 17 – Dec 31 | — | — | 50–60 days | Fairly cold-hardy; direct sow 1-3 weeks before last frost. Tolerates light frost in fall too. |
| Broccoli | Nov 19 – Dec 3 | — | Dec 17 – Dec 24 | Oct 20 – Oct 27 | 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 19 – Dec 3 | — | Dec 24 – Dec 31 | Oct 13 – Oct 20 | 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 19 – Dec 3 | — | Dec 10 – Dec 24 | Oct 13 – Oct 27 | 60–100 days | Cold-hardy; start indoors 5-7 weeks before last frost, transplant 2-4 weeks before last frost. |
| Brussels Sprouts | Nov 19 – Dec 3 | — | Dec 17 – Dec 31 | — | 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 10 – Dec 24 | — | Sep 29 – Oct 13 | 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 10 – Dec 24 | — | Oct 13 – Oct 27 | 50–65 days | Direct sow 2-4 weeks before last frost; tolerates light frost. |
| Radish | — | Dec 3 – Dec 17 | — | Nov 10 – Nov 24 | 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 10 – Dec 24 | — | Oct 13 – Oct 27 | 40–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. |
| Onion | Oct 29 – Nov 12 | — | Dec 10 – Dec 24 | — | 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 24 – Dec 8 | 240–270 days | Fall-planted crop only; not planted in spring in most climates. |
| Potato | — | Dec 10 – Dec 24 | — | — | 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 21 – Feb 4 | — | 90–120 days | Set out slips 2-4 weeks after last frost once soil is thoroughly warm (65F+); very frost/cold sensitive. |
| Asparagus | — | — | Dec 10 – Dec 24 | — | 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 26 – Dec 3 | — | Jan 14 – Jan 21 | — | 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 17 – Dec 31 | — | Oct 27 – Nov 10 | 45–70 days | Cool-season, bolts in heat; direct sow 1-3 weeks before last frost, succession sow through spring. |
| Parsley | Nov 12 – Nov 26 | — | Dec 24 – Dec 31 | — | 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 17 – Dec 31 | — | — | 40–60 days | Taprooted, does not transplant well; direct sow 1-3 weeks before last frost, succession sow through summer. |
| Oregano | Nov 12 – Nov 26 | — | Jan 7 – Jan 14 | — | 80–90 days | Perennial herb; start indoors 6-8 weeks before last frost, transplant around/just after last frost date. |
| Thyme | Nov 12 – Nov 26 | — | Jan 7 – Jan 14 | — | 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 14 – Jan 28 | — | — | 70–100 days | Direct sow 1-3 weeks after last frost once soil has warmed; taprooted, resents transplanting. |
| Zinnia | Dec 10 – Dec 17 | Jan 14 – Jan 28 | Jan 14 – Jan 21 | — | 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 26 – Dec 10 | — | Jan 14 – Jan 21 | — | 45–60 days | Frost-tender; start indoors 4-6 weeks before last frost, transplant after all frost danger has passed. |
| Cosmos | Dec 10 – Dec 17 | Jan 14 – Jan 28 | Jan 14 – Jan 21 | — | 60–90 days | Easy from direct seed 1-3 weeks after last frost; can also start indoors 3-4 weeks early. |
| Nasturtium | — | Jan 14 – Jan 28 | — | — | 50–65 days | Frost-tender, resents root disturbance; direct sow 1-3 weeks after last frost once soil has warmed. |
| Dahlia | — | — | Jan 14 – Jan 28 | — | 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 Union City, CA?
Based on 1991–2020 NOAA climate normals for the FREMONT, CA US station, the last spring frost in Union City typically falls around January 7. A cautious gardener might wait until February 7 (only a 10% chance of a later frost), while December 14 marks an earlier, higher-risk planting date.
When is the first frost in Union City, CA in fall?
The first fall frost in Union City typically arrives around December 22. To stay safe, assume frost could start as early as December 2; in milder years it can hold off until January 21.
How long is the growing season in Union City, CA?
Union City's average frost-free growing season is about 353 days, running from the typical last spring frost (January 7) to the typical first fall frost (December 22).
What USDA hardiness zone is Union City, CA in?
Union City, 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.