Santa Rosa, California: planting zone & frost dates
Santa Rosa is in USDA plant hardiness zone 9a, where the average coldest winter night reaches 20 to 25°F (-6.7 to -3.9°C). The typical last spring frost is around Mar 7 and the first fall frost around Nov 21.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Mar 29 | Nov 10 |
| Typical planning date (30% risk) | Mar 7 | Nov 21 |
| Median (50%) | Feb 25 | Dec 1 |
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 SANTA ROSA, CA (USC00047965), 0.8 mi (1.3 km) from the city center and 13 ft lower than the city center (-4 m). Record used for the 1991–2020 normals: 22 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Santa Rosa
Santa Rosa spans more than one half-zone. Share of the city's land area by zone (via its 7 ZIP codes): 9a (62%), 9b (38%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Santa Rosa
Dates are counted from the 30%-risk frost dates above (last frost Mar 7, first frost Nov 21). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Jan 10 – Jan 24 | Mar 14 – Mar 28 | — | — |
| Pepper | Dec 27 – Jan 10 | Mar 21 – Apr 4 | — | — |
| Lettuce | Jan 24 – Feb 7 | Feb 21 – Mar 14 | Feb 7 – Mar 21 | Sep 12 – Oct 10 |
| Green Beans | — | — | Mar 14 – Apr 18 | Aug 29 – Sep 12 |
| Sweet Corn | — | — | Mar 14 – Apr 11 | — |
| Zucchini & Summer Squash | Feb 7 – Feb 14 | Mar 14 – Mar 28 | Mar 14 – Apr 4 | Aug 29 – Sep 12 |
| Cucumber | Feb 7 – Feb 14 | Mar 21 – Mar 28 | Mar 14 – Apr 4 | Aug 29 – Sep 12 |
| Carrot | — | — | Feb 14 – Mar 21 | Aug 29 – Sep 12 |
| Onion | Dec 13 – Dec 27 | Feb 7 – Feb 21 | — | — |
| Potato | — | Feb 7 – Feb 28 | — | — |
| Basil | Jan 24 – Feb 7 | Mar 21 – Apr 4 | Mar 21 – Apr 11 | — |
| Spinach | — | — | Jan 24 – Feb 21 | Sep 26 – Oct 24 |
| Kale | Jan 10 – Jan 24 | Feb 7 – Feb 28 | Feb 7 – Feb 28 | Sep 12 – Oct 10 |
| Broccoli | Jan 10 – Jan 24 | Feb 21 – Mar 14 | — | Aug 29 – Sep 12 |
| Peas | — | — | Jan 24 – Feb 14 | Sep 12 – Sep 26 |
| Eggplant | Dec 27 – Jan 10 | Mar 21 – Apr 4 | — | — |
| Cabbage | Jan 10 – Jan 24 | Feb 7 – Feb 21 | — | Aug 29 – Sep 12 |
| Radish | — | — | Jan 31 – Mar 21 | Oct 10 – Nov 7 |
| Strawberry | — | Feb 7 – Feb 28 | — | — |
| Beets | — | — | Feb 14 – Mar 28 | Sep 12 – Sep 26 |
Nearby cities in California
- Napa — zone 9b, last frost Feb 27, first frost Nov 28
- Vallejo — zone 9b, last frost Mar 25, first frost Nov 12
- Richmond — zone 10a, last frost Jan 14, first frost Dec 27
- Fairfield — zone 9b, last frost Jan 28, first frost Dec 7
- Berkeley — zone 10a, last frost Jan 12, first frost Dec 25
- San Francisco — zone 10b, frost rare
More: all California cities · other zone 9a cities: San Antonio, TX, Austin, TX, Seattle, WA, Las Vegas, NV, Portland, OR, Tucson, AZ, Baton Rouge, LA, Tallahassee, FL
Santa Rosa gardening questions
When is the last frost in Santa Rosa, CA?
Plan around Mar 7. At NOAA's Santa Rosa, CA station, 0.8 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 Feb 25, and after Mar 29 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Jan 20. Springs here are erratic: 67 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 Santa Rosa, CA?
Start seeds indoors Jan 10 – Jan 24 and set transplants outside Mar 14 – Mar 28, once nights stay above 50°F and the soil is near 60°F. That leaves 259 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Santa Rosa?
About 279 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 244 days, and in 1 year in 10 it runs 319 days or more. In fall there is a 10% chance of frost by Nov 10 and a 30% chance by Nov 21. That ranks 74th longest of 84 California cities on this site.
When should I plant a fall garden in Santa Rosa?
Count back from the first fall frost (Nov 21): transplant broccoli Aug 29 – Sep 12; sow kale Sep 12 – Oct 10; sow lettuce Sep 12 – Oct 10; sow radishes Oct 10 – Nov 7. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Dec 16. How the math works: succession and fall planting.
Did Santa Rosa's hardiness zone change on the 2023 map?
Yes, but toward colder: Santa Rosa went from zone 9b (2012) to zone 9a (2023). Only about 1% of U.S. ZIP codes moved colder; these changes mostly reflect added weather stations and improved mapping methods rather than a colder climate. Why the 2023 map is warmer.
Is all of Santa Rosa in zone 9a?
No. Zone 9a covers about 62% of the city's land; the rest is in 9b (38%), measured across the city's 7 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.