Dangerous heat wave to scorch much of U.S. ahead of July Fourth, with historic highs possible

Millions across the central and eastern U.S. could face days of triple-digit heat index values.

An intense and prolonged heat wave could bring record temperatures to the central and eastern United States ahead of Independence Day celebrations.

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Nearly 142 million people were under National Weather Service heat alerts, with that number likely to grow as heat moves toward the Southeast, Midwest and Northeast.

“The latest guidance continues to strongly agree on a potentially historic heatwave across the eastern third of the country for the end of the week,” the weather service said in a forecast discussion Sunday.