Sunnyvale, California: planting zone & frost dates
Sunnyvale is in USDA plant hardiness zone 9b, where the average coldest winter night reaches 25 to 30°F (-3.9 to -1.1°C). The typical last spring frost is around Jan 18 and the first fall frost around Dec 15.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Feb 4 | Dec 3 |
| Typical planning date (30% risk) | Jan 18 | Dec 15 |
| Median (50%) | Jan 6 | Dec 23 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station MOFFETT FEDERAL AIRFIELD, CA (USW00023244), 1.8 mi (2.9 km) from the city center and 20 ft lower than the city center (-6 m). Record used for the 1991–2020 normals: 22 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Sunnyvale
Sunnyvale spans more than one half-zone. Share of the city's land area by zone (via its 4 ZIP codes): 9b (53%), 10a (47%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Sunnyvale
Dates are counted from the 30%-risk frost dates above (last frost Jan 18, first frost Dec 15). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Nov 23 – Dec 7 | Jan 25 – Feb 8 | — | — |
| Pepper | Nov 9 – Nov 23 | Feb 1 – Feb 15 | — | — |
| Lettuce Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 7 – Dec 21 | Jan 4 – Jan 25 | Dec 21 – Feb 1 | Oct 6 – Nov 3 |
| Green Beans | — | — | Jan 25 – Mar 1 | Sep 22 – Oct 6 |
| Sweet Corn | — | — | Jan 25 – Feb 22 | — |
| Zucchini & Summer Squash | Dec 21 – Dec 28 | Jan 25 – Feb 8 | Jan 25 – Feb 15 | Sep 22 – Oct 6 |
| Cucumber | Dec 21 – Dec 28 | Feb 1 – Feb 8 | Jan 25 – Feb 15 | Sep 22 – Oct 6 |
| Carrot Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 28 – Feb 1 | Sep 22 – Oct 6 |
| Onion Mild winters: fall and winter plantings are usually more reliable than spring. | Oct 26 – Nov 9 | Dec 21 – Jan 4 | — | — |
| Potato Mild winters: fall and winter plantings are usually more reliable than spring. | — | Dec 21 – Jan 11 | — | — |
| Basil | Dec 7 – Dec 21 | Feb 1 – Feb 15 | Feb 1 – Feb 22 | — |
| Spinach Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 7 – Jan 4 | Oct 20 – Nov 17 |
| Kale Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 23 – Dec 7 | Dec 21 – Jan 11 | Dec 21 – Jan 11 | Oct 6 – Nov 3 |
| Broccoli Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 23 – Dec 7 | Jan 4 – Jan 25 | — | Sep 22 – Oct 6 |
| Peas Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 7 – Dec 28 | Oct 6 – Oct 20 |
| Eggplant | Nov 9 – Nov 23 | Feb 1 – Feb 15 | — | — |
| Cabbage Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 23 – Dec 7 | Dec 21 – Jan 4 | — | Sep 22 – Oct 6 |
| Radish Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 14 – Feb 1 | Nov 3 – Dec 1 |
| Strawberry | — | Dec 21 – Jan 11 | — | — |
| Beets Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 28 – Feb 8 | Oct 6 – Oct 20 |
Nearby cities in California
- Mountain View — zone 10a, last frost Jan 18, first frost Dec 15
- Santa Clara — zone 9b, last frost Jan 26, first frost Dec 12
- Fremont — zone 9b, last frost Jan 8, first frost Dec 19
- Milpitas — zone 10a, last frost Jan 26, first frost Dec 12
- Redwood City — zone 10a, last frost Jan 31, first frost Dec 4
- San Jose — zone 9b, last frost Jan 10, first frost Dec 14
More: all California cities · other zone 9b cities: Houston, TX, Phoenix, AZ, Jacksonville, FL, San Jose, CA, Fresno, CA, Sacramento, CA, Mesa, AZ, Bakersfield, CA
Sunnyvale gardening questions
When is the last frost in Sunnyvale, CA?
Plan around Jan 18. At NOAA's Moffett Federal Airfield, CA station, 1.8 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Jan 6, and after Feb 4 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Jan 1. Springs here are erratic: 50 days separate the 90% and 10% dates, versus a median of 36 days for cities on this site, so watch the forecast rather than the calendar.
When should I plant tomatoes in Sunnyvale, CA?
Start seeds indoors Nov 23 – Dec 7 and set transplants outside Jan 25 – Feb 8, once nights stay above 50°F and the soil is near 60°F. With about 331 frost-free days, frost is not the main limit — fruit set drops when nights stay above about 75°F, so early plantings tend to do best. More: tomato planting dates by zone.
How long is the growing season in Sunnyvale?
About 353 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 323 days, and in 1 year in 10 it runs 365 days or more. In fall there is a 10% chance of frost by Dec 3 and a 30% chance by Dec 15. That ranks 35th longest of 84 California cities on this site.
When should I plant a fall garden in Sunnyvale?
Count back from the first fall frost (Dec 15): transplant broccoli Sep 22 – Oct 6; sow kale Oct 6 – Nov 3; sow lettuce Oct 6 – Nov 3; sow radishes Nov 3 – Dec 1. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Dec 31. How the math works: succession and fall planting.
Did Sunnyvale's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Sunnyvale is zone 9b on both the 2012 and the 2023 USDA maps (PRISM/OSU ZIP listings). About 42% of U.S. ZIP codes kept their half-zone in 2023. Why the 2023 map is warmer.
Is all of Sunnyvale in zone 9b?
No. Zone 9b covers about 53% of the city's land; the rest is in 10a (47%), measured across the city's 4 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.