Corona, California: planting zone & frost dates
Corona 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 29 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 21 | Dec 5 |
| Typical planning date (30% risk) | Jan 29 | Dec 19 |
| Median (50%) | Jan 9 | 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 RIVERSIDE MUNI AP, CA (USW00003171), 9.6 mi (15.4 km) from the city center and 30 ft lower than the city center (-9 m). Record used for the 1991–2020 normals: 21 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Corona
All 6 ZIP codes covering Corona are in zone 10a.
Vegetable planting calendar for Corona
Dates are counted from the 30%-risk frost dates above (last frost Jan 29, 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 4 – Dec 18 | Feb 5 – Feb 19 | — | — |
| Pepper | Nov 20 – Dec 4 | Feb 12 – Feb 26 | — | — |
| Lettuce Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 18 – Jan 1 | Jan 15 – Feb 5 | Jan 1 – Feb 12 | Oct 10 – Nov 7 |
| Green Beans | — | — | Feb 5 – Mar 12 | Sep 26 – Oct 10 |
| Sweet Corn | — | — | Feb 5 – Mar 5 | — |
| Zucchini & Summer Squash | Jan 1 – Jan 8 | Feb 5 – Feb 19 | Feb 5 – Feb 26 | Sep 26 – Oct 10 |
| Cucumber | Jan 1 – Jan 8 | Feb 12 – Feb 19 | Feb 5 – Feb 26 | Sep 26 – Oct 10 |
| Carrot Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Jan 8 – Feb 12 | Sep 26 – Oct 10 |
| Onion Mild winters: fall and winter plantings are usually more reliable than spring. | Nov 6 – Nov 20 | Jan 1 – Jan 15 | — | — |
| Potato Mild winters: fall and winter plantings are usually more reliable than spring. | — | Jan 1 – Jan 22 | — | — |
| Basil | Dec 18 – Jan 1 | Feb 12 – Feb 26 | Feb 12 – Mar 5 | — |
| Spinach Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 18 – Jan 15 | Oct 24 – Nov 21 |
| Kale Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 4 – Dec 18 | Jan 1 – Jan 22 | Jan 1 – Jan 22 | Oct 10 – Nov 7 |
| Broccoli Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 4 – Dec 18 | Jan 15 – Feb 5 | — | Sep 26 – Oct 10 |
| Peas Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 18 – Jan 8 | Oct 10 – Oct 24 |
| Eggplant | Nov 20 – Dec 4 | Feb 12 – Feb 26 | — | — |
| Cabbage Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 4 – Dec 18 | Jan 1 – Jan 15 | — | Sep 26 – Oct 10 |
| Radish Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Dec 25 – Feb 12 | Nov 7 – Dec 5 |
| Strawberry | — | Jan 1 – Jan 22 | — | — |
| Beets Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Jan 8 – Feb 19 | Oct 10 – Oct 24 |
Nearby cities in California
- Chino — zone 10a, last frost Feb 3, first frost Dec 10
- Jurupa Valley — zone 10a, last frost Jan 29, first frost Dec 19
- Chino Hills — zone 10a, last frost Feb 3, first frost Dec 10
- Ontario — zone 10a, last frost Jan 13, first frost Dec 22
- Riverside — zone 10a, last frost Jan 25, first frost Dec 15
- 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
Corona gardening questions
When is the last frost in Corona, CA?
Plan around Jan 29. At NOAA's Riverside Municipal Airport, CA station, 9.6 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 9, and after Feb 21 the risk drops to about 1 in 10. 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 Corona, CA?
Start seeds indoors Dec 4 – Dec 18 and set transplants outside Feb 5 – Feb 19, once nights stay above 50°F and the soil is near 60°F. With about 324 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 Corona?
About 362 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 319 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 28th longest of 84 California cities on this site.
When should I plant a fall garden in Corona?
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 Corona's hardiness zone change on the 2023 map?
Yes. Most of Corona was zone 9b on the 2012 map and is zone 10a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
How does Corona compare with Chino, CA?
Both are in zone 10a. The typical last spring frost in Corona (Jan 29) comes about 5 days earlier than in Chino, CA (Feb 3), 10 miles away, and the first fall frost is Dec 19 versus Dec 10. Corona sits about 219 ft higher, which explains part of the gap. The two cities use different NOAA stations.