San Mateo, California: planting zone & frost dates
San Mateo 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 3 and the first fall frost around Dec 21.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Jan 13 | Dec 11 |
| Typical planning date (30% risk) | Jan 3 | Dec 21 |
| Median (50%) | Dec 29 | Dec 26 |
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 SAN FRANCISCO INTL AP, CA (USW00023234), 5.0 mi (8.1 km) from the city center and 3 ft lower than the city center (-1 m). Record used for the 1991–2020 normals: 26 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across San Mateo
All 4 ZIP codes covering San Mateo are in zone 10a.
Vegetable planting calendar for San Mateo
Dates are counted from the 30%-risk frost dates above (last frost Jan 3, first frost Dec 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 | Nov 8 – Nov 22 | Jan 10 – Jan 24 | — | — |
| Pepper | Oct 25 – Nov 8 | Jan 17 – Jan 31 | — | — |
| Lettuce Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 22 – Dec 6 | Dec 20 – Jan 10 | Dec 6 – Jan 17 | Oct 12 – Nov 9 |
| Green Beans | — | — | Jan 10 – Feb 14 | Sep 28 – Oct 12 |
| Sweet Corn | — | — | Jan 10 – Feb 7 | — |
| Zucchini & Summer Squash | Dec 6 – Dec 13 | Jan 10 – Jan 24 | Jan 10 – Jan 31 | Sep 28 – Oct 12 |
| Cucumber | Dec 6 – Dec 13 | Jan 17 – Jan 24 | Jan 10 – Jan 31 | Sep 28 – Oct 12 |
| Carrot Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 13 – Jan 17 | Sep 28 – Oct 12 |
| Onion Mild winters: fall and winter plantings are usually more reliable than spring. | Oct 11 – Oct 25 | Dec 6 – Dec 20 | — | — |
| Potato Mild winters: fall and winter plantings are usually more reliable than spring. | — | Dec 6 – Dec 27 | — | — |
| Basil | Nov 22 – Dec 6 | Jan 17 – Jan 31 | Jan 17 – Feb 7 | — |
| Spinach Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Nov 22 – Dec 20 | Oct 26 – Nov 23 |
| Kale Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 8 – Nov 22 | Dec 6 – Dec 27 | Dec 6 – Dec 27 | Oct 12 – Nov 9 |
| Broccoli Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 8 – Nov 22 | Dec 20 – Jan 10 | — | Sep 28 – Oct 12 |
| Peas Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Nov 22 – Dec 13 | Oct 12 – Oct 26 |
| Eggplant | Oct 25 – Nov 8 | Jan 17 – Jan 31 | — | — |
| Cabbage Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 8 – Nov 22 | Dec 6 – Dec 20 | — | Sep 28 – Oct 12 |
| Radish Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Nov 29 – Jan 17 | Nov 9 – Dec 7 |
| Strawberry | — | Dec 6 – Dec 27 | — | — |
| Beets Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 13 – Jan 24 | Oct 12 – Oct 26 |
Nearby cities in California
- Redwood City — zone 10a, last frost Jan 31, first frost Dec 4
- Alameda — zone 10a, last frost Jan 22, first frost Dec 10
- San Leandro — zone 10a, last frost Jan 22, first frost Dec 10
- Daly City — zone 10a, last frost Jan 23, first frost Dec 12
- Hayward — zone 10a, last frost Jan 12, first frost Dec 17
- Oakland — zone 10a, frost rare
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 Mateo gardening questions
When is the last frost in San Mateo, CA?
Plan around Jan 3. At NOAA's San Francisco Int'l Airport, CA station, 5.0 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 Dec 29, and after Jan 13 the risk drops to about 1 in 10. The 90% and 10% dates are 33 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in San Mateo, CA?
Start seeds indoors Nov 8 – Nov 22 and set transplants outside Jan 10 – Jan 24, once nights stay above 50°F and the soil is near 60°F. With about 352 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 Mateo?
About 365 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 362 days, and in 1 year in 10 it runs 365 days or more. In fall there is a 10% chance of frost by Dec 11 and a 30% chance by Dec 21. That ranks 19th longest of 84 California cities on this site.
When should I plant a fall garden in San Mateo?
Count back from the first fall frost (Dec 21): transplant broccoli Sep 28 – Oct 12; sow kale Oct 12 – Nov 9; sow lettuce Oct 12 – Nov 9; sow radishes Nov 9 – Dec 7. How the math works: succession and fall planting.
Did San Mateo's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, San Mateo 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 Mateo compare with Redwood City, CA?
Both are in zone 10a. The typical last spring frost in San Mateo (Jan 3) comes about 28 days earlier than in Redwood City, CA (Jan 31), 6 miles away, and the first fall frost is Dec 21 versus Dec 4. The two cities use different NOAA stations.