Sizzling heat persisted over much of the United States on Tuesday on the eve of the Fourth of July, prompting many communities to rethink or cancel their festivities on the US national holiday.

The heat wave, plus hurricane-like storms that struck the Mid-Atlantic on Friday, has left at least 19 dead and 1.8 million people in 11 states from Indiana to Delaware still without power, CNN reported on its website.

"The heat wave continues for a large portion of the central and eastern United States, with high temperatures this afternoon forecast to be 10-15 degrees above normal," the National Weather Service.

"Combined with high levels of humidity, this will create dangerous heat index values as high as 100-110 degrees (up to 43.3 degrees Celsius) for locations such as Minneapolis, Chicago, Kansas City and St. Louis," it said.

In the Washington area, where utilities struggled to restore electricity to a reported 116,000 homes and businesses four days after Friday's storms, at least four suburbs abandoned plans for Fourth of July fireworks shows.

Cancelations were reported in many other states as well, from Maryland to Indiana as well as Colorado where wildfires last week left two dead and destroyed nearly 350 homes.

"We are very, very concerned about Independence Day this year," said Ohio Fire Marshal Larry Flowers, quoted in the Cleveland Plain Dealer newspaper. "With the very dry temps, fireworks become even more dangerous."

On Accuweather.com, meteorologist Alex Sosnowski warned of the risk of "fast-moving, gusty storms" later Tuesday, followed by yet more high temperatures and potential storms on Wednesday.