The temperature that is considered an emergency for HVAC (Heating, Ventilation, and Air Conditioning) systems varies depending on several factors such as the location, building size, and occupancy. Generally, temperatures above 90°F or below 55°F can be considered an emergency, as they can lead to health and safety concerns, equipment failure, and even structural damage. It is important to have regular maintenance and monitoring of HVAC systems to prevent emergencies and ensure optimal performance.