The short answer
Air conditioning gets very different treatment than heat under landlord-tenant law. Heat is almost universally an essential service a landlord must provide; air conditioning is much more often optional unless it was already part of what you rented, your lease promises it, or your city or state specifically requires it.
Where AC is provided but not required from scratch
Several states address air conditioning directly, and the pattern is consistent: if a working air conditioning system already came with the unit, your landlord generally has to keep it working, under the same category of duty as heat or hot water. Arizona's law puts air conditioning in the same sentence as heat, water, and other essential services — a landlord cannot "deliberately or negligently" fail to supply it "where such units are installed and offered" (A.R.S. § 33-1364). That phrase matters: the duty applies because the AC was already offered as part of the unit, not because state law requires every rental to have it.
Where AC is explicitly not required
Maryland's emergency-repair law goes the other direction and says so in plain language: it lists "the absence of air conditioning" as one of the conditions presumed not to be a dangerous defect that triggers a landlord's repair duty, alongside things like the lack of fresh paint or carpet (Md. Code, Real Prop. § 8-211(e)(2)(iv)). In a state with that kind of rule, a landlord who never provided AC generally has no legal obligation to install it, even in a heat wave.
A middle position: required only for newer leases
Arkansas illustrates a third approach. Any lease signed or renewed there after November 1, 2021 must include, among other basics like running hot and cold water and a sound roof, "existing heat and A/C" as a condition the landlord has to maintain (Ark. Code Ann. § 18-17-502(a)). Notice the word "existing" — this still isn't a mandate to install air conditioning where none exists; it's a requirement to keep already-installed AC working, the same principle as Arizona's rule, just written into a broader list of newer-lease habitability basics. Rules like this are also a reminder that state law changes over time, so what applied to your last apartment isn't necessarily what applies to your current one.
What your lease actually promises
Because state defaults vary this much, your lease terms end up doing a lot of the work. If your unit has a window unit or central air listed in your lease or included when you toured the apartment, that's typically treated as part of what you're renting, and your landlord has to maintain it like any other included appliance. If the lease is silent and there's no AC installed, you're mostly relying on whatever your specific state or city requires — and plenty of places require neither.
Central air and a window unit can also be treated differently in practice, even under the same lease. A landlord-installed central system is usually unambiguously part of the unit. A window unit is more likely to be treated as the tenant's own property if the tenant brought it, in which case the landlord has no duty to maintain it at all — check whether your lease or move-in inventory specifies who owns any AC equipment already in the unit.
Check local rules too
Some cities and counties have their own housing codes that go further than state law, including on extreme-heat protections, especially for older or more vulnerable tenants. These are local rules that vary block by block, so they're not something a national article can name accurately — check your city or county's housing or code enforcement department directly, and ask specifically about air conditioning or extreme-heat requirements for rentals.
If your unit gets dangerously hot
Even where AC itself isn't required, a rental that becomes dangerously hot because of a landlord's neglect — broken windows that won't open, no working ventilation, or a maintenance issue that traps heat — can still be a habitability problem under your state's general "fit and habitable" standard, separate from the AC question specifically. Document the indoor temperature, the outdoor conditions, and any health effects, and report it in writing the same way you would any other repair.
This distinction matters in practice: "my apartment doesn't have AC" and "my apartment is unsafely hot because something is broken" are two different complaints, even though they can feel identical on a bad day. The first is usually a losing argument unless your lease or state says otherwise. The second is a repair complaint like any other, and it's worth framing it that way in your written notice — describe the malfunction (a window painted shut, a broken exhaust fan, a ventilation duct that's blocked) rather than just the temperature, since that's what ties it back to your landlord's ordinary repair duty.
Honestkey™ can review your lease to check whether AC was actually part of what you're renting, and whether your state's general habitability rules apply to your specific situation.