Alhambra, California: planting zone & frost dates
Alhambra 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 13 and the first fall frost around Dec 28.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Jan 28 | Dec 18 |
| Typical planning date (30% risk) | Jan 13 | Dec 28 |
| Median (50%) | Jan 4 | Jan 2 |
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 GABRIEL FIRE DEPT, CA (USC00047785), 2.1 mi (3.3 km) from the city center and 98 ft lower than the city center (-30 m). Record used for the 1991–2020 normals: 18 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Alhambra
Alhambra spans more than one half-zone. Share of the city's land area by zone (via its 2 ZIP codes): 10a (57%), 10b (43%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Alhambra
Dates are counted from the 30%-risk frost dates above (last frost Jan 13, first frost Dec 28). 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 18 – Dec 2 | Jan 20 – Feb 3 | — | — |
| Pepper | Nov 4 – Nov 18 | Jan 27 – Feb 10 | — | — |
| Lettuce Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 2 – Dec 16 | Dec 30 – Jan 20 | Dec 16 – Jan 27 | Oct 19 – Nov 16 |
| Green Beans | — | — | Jan 20 – Feb 24 | Oct 5 – Oct 19 |
| Sweet Corn | — | — | Jan 20 – Feb 17 | — |
| Zucchini & Summer Squash | Dec 16 – Dec 23 | Jan 20 – Feb 3 | Jan 20 – Feb 10 | Oct 5 – Oct 19 |
| Cucumber | Dec 16 – Dec 23 | Jan 27 – Feb 3 | Jan 20 – Feb 10 | Oct 5 – Oct 19 |
| Carrot Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 23 – Jan 27 | Oct 5 – Oct 19 |
| Onion Mild winters: fall and winter plantings are usually more reliable than spring. | Oct 21 – Nov 4 | Dec 16 – Dec 30 | — | — |
| Potato Mild winters: fall and winter plantings are usually more reliable than spring. | — | Dec 16 – Jan 6 | — | — |
| Basil | Dec 2 – Dec 16 | Jan 27 – Feb 10 | Jan 27 – Feb 17 | — |
| Spinach Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 2 – Dec 30 | Nov 2 – Nov 30 |
| Kale Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 18 – Dec 2 | Dec 16 – Jan 6 | Dec 16 – Jan 6 | Oct 19 – Nov 16 |
| Broccoli Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 18 – Dec 2 | Dec 30 – Jan 20 | — | Oct 5 – Oct 19 |
| Peas Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 2 – Dec 23 | Oct 19 – Nov 2 |
| Eggplant | Nov 4 – Nov 18 | Jan 27 – Feb 10 | — | — |
| Cabbage Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 18 – Dec 2 | Dec 16 – Dec 30 | — | Oct 5 – Oct 19 |
| Radish Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 9 – Jan 27 | Nov 16 – Dec 14 |
| Strawberry | — | Dec 16 – Jan 6 | — | — |
| Beets Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 23 – Feb 3 | Oct 19 – Nov 2 |
Nearby cities in California
- Pasadena — zone 10a, last frost Jan 14, first frost Jan 1
- El Monte — zone 10b, last frost Jan 13, first frost Dec 28
- Downey — zone 10b, frost rare
- Glendale — zone 10a, last frost Jan 14, first frost Jan 1
- South Gate — zone 10b, frost rare
- Whittier — zone 10b, 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
Alhambra gardening questions
When is the last frost in Alhambra, CA?
Plan around Jan 13. At NOAA's San Gabriel Fire Dept, CA station, 2.1 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 4, and after Jan 28 the risk drops to about 1 in 10. The 90% and 10% dates are 40 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Alhambra, CA?
Start seeds indoors Nov 18 – Dec 2 and set transplants outside Jan 20 – Feb 3, once nights stay above 50°F and the soil is near 60°F. With about 349 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 Alhambra?
About 365 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 360 days, and in 1 year in 10 it runs 365 days or more. In fall there is a 10% chance of frost by Dec 18 and a 30% chance by Dec 28. That ranks 25th longest of 84 California cities on this site.
When should I plant a fall garden in Alhambra?
Count back from the first fall frost (Dec 28): transplant broccoli Oct 5 – Oct 19; sow kale Oct 19 – Nov 16; sow lettuce Oct 19 – Nov 16; sow radishes Nov 16 – Dec 14. How the math works: succession and fall planting.
Did Alhambra's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Alhambra 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.
Is all of Alhambra in zone 10a?
No. Zone 10a covers about 57% of the city's land; the rest is in 10b (43%), measured across the city's 2 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.