Heat is required; cooling generally isn’t
California state law does not require landlords to provide air conditioning. The habitability standard requires heat, but not cooling — so there is no general statewide rule that a rental have working AC.
This surprises many tenants, because heat is required but AC is not. The reason is that the state's list of what makes a home livable includes heating facilities and does not mention air conditioning. As a baseline, AC is treated as an amenity rather than a legal necessity.
Local ordinances can add requirements in some areas, and extreme-heat protections are a growing topic as summers get hotter. What can still matter most, though, is whether your landlord agreed to provide AC in the first place — because providing it can create a duty to maintain it. If your landlord promised AC and now will not repair it, a free review can help you understand your rights.
This is general information about California tenant rights, not legal advice. Every situation is different.