Walnut, CA frost dates
Frost is light and occasional here — typically a few cold nights around midwinter (about 3 a year). Cover tender plants when frost is forecast.
How Walnut compares
- In a typical year, frost nights in Walnut fall between December 28 and January 8. In 1 year in 10 the first frost comes as early as December 5, or the last frost as late as February 18.
- Walnut shares its weather station with Diamond Bar, CA, 5 km away, so the two have the same frost dates.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | December 14 |
| 50% (median) | January 8 |
| 10% (safe for tender plants) | February 18 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | December 5 |
| 50% (median) | December 28 |
| 90% (late) | February 2 |
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
Walnut, 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 Pomona/Fairplex, CA weather station, 11 km away (elevation 1,001 ft (305 m)).
ZIP codes in Walnut: 91788 91789
Frost dates near Walnut
- Diamond Bar Jan 8 · Dec 28
- Rowland Heights rare frost
- West Covina Jan 8 · Dec 28
- Covina Jan 8 · Dec 28
- La Puente Jan 4 · Jan 2
- City Of Industry Jan 4 · Jan 2
- Hacienda Heights rare frost
- San Dimas Jan 8 · Dec 28
- Brea rare frost
- Pomona Jan 8 · Dec 28
Frequently asked questions
When is the last frost in Walnut, CA?
The median last spring frost in Walnut, CA is January 8. There is still about a 10% chance of frost after February 18, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Walnut, CA?
The median first fall frost is December 28, with about a 10% chance of frost before December 5.
How long is the growing season in Walnut, CA?
About 354 days between the median last spring frost and first fall frost.
What planting zone is Walnut, CA?
Walnut, CA is in USDA hardiness zone 10a.