Every air conditioner is rated for performance at a specific ambient temperature range, and cooling output naturally declines as outdoor temperature rises above that design point. This happens because the condenser has to reject heat into the surrounding air, and the hotter that air already is, the smaller the temperature difference the condenser has to work with, forcing the compressor to run at higher pressures to achieve the same heat transfer.
On extremely hot days, a unit that cools a room comfortably in moderate weather may struggle to reach the same set temperature, which is a normal physical limitation rather than necessarily a fault. Humidity compounds this effect, since a cooling system also has to remove moisture from the air alongside lowering temperature, and highly humid conditions increase the total load on the system beyond what temperature alone would suggest.
Manufacturers typically specify a maximum outdoor operating temperature beyond which the unit's safety systems may reduce compressor speed or shut it down entirely to prevent damage from excessive pressure. Understanding this relationship helps in setting realistic expectations for cooling performance during unusually hot weather and in recognizing when reduced output is a normal response to conditions rather than a component failure needing repair.