What is a dangerous heat index number?

A dangerous heat index number is typically considered to be 80°F (27°C) or higher, with more severe risks noted at 90°F (32°C) and above. At these levels, the combination of heat and humidity can lead to heat-related illnesses, such as heat exhaustion or heat stroke, especially for vulnerable populations. The National Weather Service often issues heat advisories when the heat index reaches these dangerous levels. It's crucial to take precautions, such as staying hydrated and avoiding prolonged outdoor activities in extreme heat.