San Marcos, California: planting zone & frost dates
San Marcos is in USDA plant hardiness zone 10a, where the average coldest winter night reaches 30 to 35°F (-1.1 to 1.7°C). The typical last spring frost is around Jan 14 and the first fall frost around Dec 23.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Feb 4 | Dec 8 |
| Typical planning date (30% risk) | Jan 14 | Dec 23 |
| Median (50%) | Jan 2 | Dec 30 |
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 ESCONDIDO #2, CA (USC00042863), 4.7 mi (7.5 km) from the city center and 46 ft lower than the city center (-14 m). Record used for the 1991–2020 normals: 19 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across San Marcos
All 3 ZIP codes covering San Marcos are in zone 10a.
Vegetable planting calendar for San Marcos
Dates are counted from the 30%-risk frost dates above (last frost Jan 14, first frost Dec 23). 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 19 – Dec 3 | Jan 21 – Feb 4 | — | — |
| Pepper | Nov 5 – Nov 19 | Jan 28 – Feb 11 | — | — |
| Lettuce Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 3 – Dec 17 | Dec 31 – Jan 21 | Dec 17 – Jan 28 | Oct 14 – Nov 11 |
| Green Beans | — | — | Jan 21 – Feb 25 | Sep 30 – Oct 14 |
| Sweet Corn | — | — | Jan 21 – Feb 18 | — |
| Zucchini & Summer Squash | Dec 17 – Dec 24 | Jan 21 – Feb 4 | Jan 21 – Feb 11 | Sep 30 – Oct 14 |
| Cucumber | Dec 17 – Dec 24 | Jan 28 – Feb 4 | Jan 21 – Feb 11 | Sep 30 – Oct 14 |
| Carrot Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 24 – Jan 28 | Sep 30 – Oct 14 |
| Onion Mild winters: fall and winter plantings are usually more reliable than spring. | Oct 22 – Nov 5 | Dec 17 – Dec 31 | — | — |
| Potato Mild winters: fall and winter plantings are usually more reliable than spring. | — | Dec 17 – Jan 7 | — | — |
| Basil | Dec 3 – Dec 17 | Jan 28 – Feb 11 | Jan 28 – Feb 18 | — |
| Spinach Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 3 – Dec 31 | Oct 28 – Nov 25 |
| Kale Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 19 – Dec 3 | Dec 17 – Jan 7 | Dec 17 – Jan 7 | Oct 14 – Nov 11 |
| Broccoli Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 19 – Dec 3 | Dec 31 – Jan 21 | — | Sep 30 – Oct 14 |
| Peas Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 3 – Dec 24 | Oct 14 – Oct 28 |
| Eggplant | Nov 5 – Nov 19 | Jan 28 – Feb 11 | — | — |
| Cabbage Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 19 – Dec 3 | Dec 17 – Dec 31 | — | Sep 30 – Oct 14 |
| Radish Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 10 – Jan 28 | Nov 11 – Dec 9 |
| Strawberry | — | Dec 17 – Jan 7 | — | — |
| Beets Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 24 – Feb 4 | Oct 14 – Oct 28 |
Nearby cities in California
- Vista — zone 10a, last frost Feb 24, first frost Dec 24
- Escondido — zone 10a, last frost Jan 14, first frost Dec 23
- Carlsbad — zone 10a, frost rare
- Oceanside — zone 10a, last frost Feb 4, first frost Dec 1
- San Diego — zone 10b, frost rare
- Temecula — zone 9b, last frost Feb 14, first frost Jan 3
More: all California cities · other zone 10a cities: Los Angeles, CA, Oakland, CA, Tampa, FL, Orlando, FL, Riverside, CA, Corpus Christi, TX, Port St. Lucie, FL, Scottsdale, AZ
San Marcos gardening questions
When is the last frost in San Marcos, CA?
Plan around Jan 14. At NOAA's Escondido #2, CA station, 4.7 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 2, and after Feb 4 the risk drops to about 1 in 10. Springs here are erratic: 52 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 San Marcos, CA?
Start seeds indoors Nov 19 – Dec 3 and set transplants outside Jan 21 – Feb 4, once nights stay above 50°F and the soil is near 60°F. With about 343 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 San Marcos?
About 365 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 339 days, and in 1 year in 10 it runs 365 days or more. In fall there is a 10% chance of frost by Dec 8 and a 30% chance by Dec 23. That ranks 22nd longest of 84 California cities on this site.
When should I plant a fall garden in San Marcos?
Count back from the first fall frost (Dec 23): transplant broccoli Sep 30 – Oct 14; sow kale Oct 14 – Nov 11; sow lettuce Oct 14 – Nov 11; sow radishes Nov 11 – Dec 9. How the math works: succession and fall planting.
Did San Marcos's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, San Marcos is zone 10a 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.
How does San Marcos compare with Vista, CA?
Both are in zone 10a. The typical last spring frost in San Marcos (Jan 14) comes about 41 days earlier than in Vista, CA (Feb 24), 6 miles away, and the first fall frost is Dec 23 versus Dec 24. San Marcos sits about 199 ft higher, which explains part of the gap. The two cities use different NOAA stations.