July 02, 2026 | Source: Scientific American | by Claire Cameron

As Americans come out to commemorate the nation’s 250th birthday on Saturday, the temperatures across huge swaths of the nation will be anything but celebratory. An intense heat wave is settling over the East and Central U.S., exposing millions to temperatures above the seasonal average and putting them at risk of heat-related illnesses.

Up and down the East Coast and the Central U.S., the mercury could surpass 100 degrees Fahrenheit (38 degrees Celsius), with some places, such as New York City, potentially feeling as hot as 115 degrees F (46 degrees C) during the day. The simplest way to stay safe is to remain indoors in air-conditioned spaces with easy access to cold water—both for drinking, and for showering or wetting towels to cool your body. But that won’t work for everyone.

Most public health messaging during a heat wave focuses on two heat-related illnesses: heat exhaustion and heat stroke. And for good reason: heat stroke, the more serious condition, can occur when the body’s internal temperature rises above 104 degrees F (40 degrees C) or by extreme dehydration. Heat stroke can be fatal without immediate medical attention.