Cal. Civ. Code § 8-122

(a) (1) This section applies only to residential rental units in apartment buildings with 10 or more individual dwelling units.

(2) This section does not apply to a residential rental unit that is located on property listed on the National Register of Historic Places.

(b) A landlord shall provide air–conditioning in each residential unit in accordance with subsection (c) of this section as follows:

(1) Beginning June 1, 2026, for newly constructed residential rental units;

(2) Beginning June 1, 2026, for residential rental units where, at any time on or after January 1, 2025:

(i) The landlord equipped the unit with air–conditioning or provided air–conditioning; or

(ii) A lease required the landlord to provide air–conditioning for the unit; and

(3) Beginning October 1, 2026, for residential rental units that undergo renovation that includes the replacement or substantial upgrade of electrical systems or heating systems.

(c) Except as otherwise necessary for purposes of reasonable maintenance and repair, each year from June 1 to September 30, both inclusive, a landlord shall provide air–conditioning in each residential unit as follows:

(1) For an air–conditioning system that is not under the control of the tenant, the landlord shall maintain the temperature in the unit at not greater than 80 degrees Fahrenheit at 3 feet above the floor level in each habitable space in the unit; and

(2) For an air–conditioning system that is under the control of the tenant, the landlord shall ensure that the air–conditioning system is in good working order and is capable of maintaining the temperature in the unit at not greater than 80 degrees Fahrenheit at 3 feet above the floor level in each habitable space in the unit.