What zone 10b means
In zone 10b, the average of the coldest night of each winter (1991 to 2020) is 35 to 40°F (2 to 4°C). Some winters will be colder than that and some milder: the zone is an average, not the coldest temperature ever recorded. When a plant tag lists a zone range that includes 10b, the plant should survive a typical winter here. If you are in the "a" half, you are in the colder part of the zone.
Zone 10b next to its neighbors
Zone 10a, one half zone colder, averages 30 to 35°F (-1 to 2°C). Zone 11a, one half zone warmer, averages 40 to 45°F (4 to 7°C). On the 2023 map, about half the country moved to the next warmer half zone compared with 2012, so some gardens that were in 10a are now in 10b.
Using zone 10b when you shop
Look for the hardiness range on plant tags and in catalogs. A plant listed for "zones 8 to 12" includes zone 10b. If the range stops just above you, choose a sheltered spot, mulch roots before winter or grow it in a pot. Remember that zones describe winter cold only; heat, rainfall and soil decide the rest. How to read a plant tag.
States with the most zone 10b ZIP codes
Cities in zone 10b
Frequently asked questions
What does zone 10b mean?
Zone 10b covers places where the average coldest winter night is 35 to 40°F (2 to 4°C). On the 2023 USDA map, 752 ZIP codes are in zone 10b.
What is the difference between zone 10a and 10b?
Each 10°F zone is split into two 5°F half zones. "a" is the colder half and "b" the warmer half. Zone 10a averages 30 to 35°F (-1 to 2°C); zone 10b averages 35 to 40°F (2 to 4°C).
Source: 2023 USDA Plant Hardiness Zone Map ZIP code listings, PRISM Climate Group, Oregon State University; USDA ARS. Not the official USDA map.