Pomona, California: planting zone & frost dates
Pomona 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 26 and the first fall frost around Dec 19.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Feb 18 | Dec 5 |
| Typical planning date (30% risk) | Jan 26 | Dec 19 |
| Median (50%) | Jan 8 | Dec 28 |
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 POMONA/FAIRPLEX, CA (USC00047050), 1.6 mi (2.6 km) from the city center and 154 ft higher than the city center (+47 m). Record used for the 1991–2020 normals: 16 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Pomona
All 4 ZIP codes covering Pomona are in zone 10a.
Vegetable planting calendar for Pomona
Dates are counted from the 30%-risk frost dates above (last frost Jan 26, first frost Dec 19). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Dec 1 – Dec 15 | Feb 2 – Feb 16 | — | — |
| Pepper | Nov 17 – Dec 1 | Feb 9 – Feb 23 | — | — |
| Lettuce Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 15 – Dec 29 | Jan 12 – Feb 2 | Dec 29 – Feb 9 | Oct 10 – Nov 7 |
| Green Beans | — | — | Feb 2 – Mar 9 | Sep 26 – Oct 10 |
| Sweet Corn | — | — | Feb 2 – Mar 2 | — |
| Zucchini & Summer Squash | Dec 29 – Jan 5 | Feb 2 – Feb 16 | Feb 2 – Feb 23 | Sep 26 – Oct 10 |
| Cucumber | Dec 29 – Jan 5 | Feb 9 – Feb 16 | Feb 2 – Feb 23 | Sep 26 – Oct 10 |
| Carrot Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Jan 5 – Feb 9 | Sep 26 – Oct 10 |
| Onion Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 3 – Nov 17 | Dec 29 – Jan 12 | — | — |
| Potato Mild winters: fall and winter plantings are usually more reliable than spring. | — | Dec 29 – Jan 19 | — | — |
| Basil | Dec 15 – Dec 29 | Feb 9 – Feb 23 | Feb 9 – Mar 2 | — |
| Spinach Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 15 – Jan 12 | Oct 24 – Nov 21 |
| Kale Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 1 – Dec 15 | Dec 29 – Jan 19 | Dec 29 – Jan 19 | Oct 10 – Nov 7 |
| Broccoli Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 1 – Dec 15 | Jan 12 – Feb 2 | — | Sep 26 – Oct 10 |
| Peas Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 15 – Jan 5 | Oct 10 – Oct 24 |
| Eggplant | Nov 17 – Dec 1 | Feb 9 – Feb 23 | — | — |
| Cabbage Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 1 – Dec 15 | Dec 29 – Jan 12 | — | Sep 26 – Oct 10 |
| Radish Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 22 – Feb 9 | Nov 7 – Dec 5 |
| Strawberry | — | Dec 29 – Jan 19 | — | — |
| Beets Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Jan 5 – Feb 16 | Oct 10 – Oct 24 |
Nearby cities in California
- Upland — zone 10a, last frost Jan 26, first frost Dec 19
- Chino Hills — zone 10a, last frost Feb 3, first frost Dec 10
- Chino — zone 10a, last frost Feb 3, first frost Dec 10
- West Covina — zone 10a, last frost Jan 13, first frost Dec 28
- Ontario — zone 10a, last frost Jan 13, first frost Dec 22
- Anaheim — 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
Pomona gardening questions
When is the last frost in Pomona, CA?
Plan around Jan 26. At NOAA's Pomona/fairplex, CA station, 1.6 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 8, and after Feb 18 the risk drops to about 1 in 10. Springs here are erratic: 66 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 Pomona, CA?
Start seeds indoors Dec 1 – Dec 15 and set transplants outside Feb 2 – Feb 16, once nights stay above 50°F and the soil is near 60°F. With about 327 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 Pomona?
About 354 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 315 days, and in 1 year in 10 it runs 365 days or more. In fall there is a 10% chance of frost by Dec 5 and a 30% chance by Dec 19. That ranks 32nd longest of 84 California cities on this site.
When should I plant a fall garden in Pomona?
Count back from the first fall frost (Dec 19): transplant broccoli Sep 26 – Oct 10; sow kale Oct 10 – Nov 7; sow lettuce Oct 10 – Nov 7; sow radishes Nov 7 – Dec 5. How the math works: succession and fall planting.
Did Pomona's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Pomona 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 Pomona compare with Chino, CA?
Both are in zone 10a. The typical last spring frost in Pomona (Jan 26) comes about 8 days earlier than in Chino, CA (Feb 3), 8 miles away, and the first fall frost is Dec 19 versus Dec 10. Pomona sits about 229 ft higher, which explains part of the gap. The two cities use different NOAA stations.