Wide swaths of the United States are now preparing to face a second day of heat waves that have pushed temperatures to record levels in many regions, prompting meteorologists to warn of the dangers of drought and exposure to sunlight.

And the National Weather Service said about 100 million Americans, from New York in the east to Las Vegas on the west coast, could see dangerous temperatures above 38 degrees Celsius and be the target of warnings and advisories to heat on the day. He advised residents to stay at home, avoid exercise and stay hydrated by drinking plenty of fluids.

The administration said temperatures are now expected to break daily records in Texas, Louisiana and Arkansas.

Air pollution is another health hazard during heat waves. Pollution from the power grid can double when power plants operate at full capacity during heatwaves.

Irkut Corporation, the operator of the Texas power grid, this week asked state environmental regulators to act alone when power plants exceed pollution limits. Texas’ power grid needs power plants to run at maximum capacity to meet the growing demand for electricity as the state’s temperatures rise.