C is the record low. Subtropical plants thrive. Rain is plentiful all year, heaviest in summer and early fall. Many plants from tropical and subtropical Africa and South America are well adapted here. Azaleas, camellias, many subtropicals flourish.
Summers are hot.
For more information, consult Sunset's National Garden Book and Western Garden Book. Summers are muggy and warm to hot. Summers can be truly hot and humid. Late frosts are common. May to mid-Oct., with rainfall throughout.