Health officials say an oppressive heat wave that has blanketed large swaths of the United States has contributed to the deaths of at least six people.
Various news outlets have reported heat-related deaths in the states of Maryland, Arizona and Arkansas.
The National Weather Service warned a "dangerous heat wave" paired with high humidity in the United States over the weekend could quickly cause heat stress or heat stroke, if precautions are not taken.
Events were canceled throughout the nation, from festivals and concerts to sporting events.
The NWS said temperatures would remain warm at night, in the upper 70s to low 80s, with more heat on the way Sunday for the East Coast. The agency also advised people to check in on relatives and friends, especially the elderly.
During a span of three days in July 1995, more than 700 people died in Chicago, when temperatures rose above 36 degrees Celsius. Many of those who died were poor or elderly with no access to air conditioning. Many also lived alone.
Despite the warnings, one runner in the nation's capital planned to head out for a run early Saturday. "It's brutal,'' Jeffrey Glickman, 37, said, adding, "You just have to power through it the best you can."
Temperatures have been rising in cities from the Midwest to the East Coast because of a high pressure system that has trapped the warm air. City officials are allowing public pools to stay open longer and municipalities are issuing advisories to inform the public about how best to deal with the heat.