Frost dates for 94552 — Castro Valley, CA
Frost is light and occasional here — typically a few cold nights around midwinter (about 1 a year). Cover tender plants when frost is forecast.
How Castro Valley compares
- In a typical year, frost nights in Castro Valley fall between December 25 and January 2. In 1 year in 10 the first frost comes as early as December 6, or the last frost as late as January 27.
- Castro Valley shares its weather station with Hayward, CA, 6 km away, so the two have the same frost dates.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | December 13 |
| 50% (median) | January 2 |
| 10% (safe for tender plants) | January 27 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | December 6 |
| 50% (median) | December 25 |
| 90% (late) | January 20 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Gardening where frost is rare
Castro Valley, CA only freezes on a few winter nights, so the usual "plant after the last frost" rule doesn't apply. Heat and rainfall decide the seasons instead:
- Cool-season crops (lettuce, broccoli, peas, carrots) grow best from fall through late winter.
- Warm-season crops (tomatoes, peppers, beans, squash) do best planted in late winter to spring, and again in late summer for a fall crop — midsummer heat can stop tomatoes setting fruit.
- Heat lovers (okra, sweet potatoes, melons) can be planted through spring and early summer.
About these dates
Based on 1991–2020 NOAA climate normals for the Hayward Air Terminal, CA weather station, 9 km away (elevation 43 ft (13 m)).
ZIP codes in Castro Valley: 94546 94552
Frost dates near Castro Valley
- Hayward Jan 2 · Dec 25
- San Lorenzo Jan 2 · Dec 25
- San Leandro Jan 2 · Dec 25
- Moraga Mar 8 · Dec 22
- Dublin Feb 15 · Dec 2
- San Ramon Feb 15 · Dec 2
- Union City Jan 7 · Dec 22
- Pleasanton Feb 15 · Dec 2
Frequently asked questions
When is the last frost in Castro Valley, CA?
The median last spring frost in Castro Valley, CA is January 2. There is still about a 10% chance of frost after January 27, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Castro Valley, CA?
The median first fall frost is December 25, with about a 10% chance of frost before December 6.
How long is the growing season in Castro Valley, CA?
About 357 days between the median last spring frost and first fall frost.
What planting zone is Castro Valley, CA?
Castro Valley, CA is in USDA hardiness zone 9b.