A persisting heat wave is roasting much of the United States, with the U.S. National Weather service warning Monday the extreme weather condition is expected to last until at least Thursday.

"A heat wave continues from the Midwest to the Mid-Atlantic and Northeast through the 4th of July holiday," the NWS said in a warning, illustrating with a map that the New England region and Southern California are the worst affected regions.

"Under the influence of a strong subtropical high pressure system, temperatures will remain more than 10 degrees above normal across New England," the NWS said.

By Monday, in major cities such as Washington, Baltimore, Philadelphia and New York City, the heat index, which is a combination of air temperature and humidity, surpassed 38 degrees Celsius.

Even during night time the air temperature failed to drop below 27 degrees Celsius, a level that can lead to heat related diseases such as heat strokes.

Many cities along the U.S. east coast are in their fourth or fifth consecutive day with temperatures above 32 degrees Celsius, as three consecutive days above the threshold is considered a heat wave.

The extreme and dangerous weather came as U.S. media reported Monday that a website affiliated to the U.S. Centers for Disease Control and Prevention has removed the term "climate change" from its website, raising concerns over the motive for such a move.

The Centers for Disease Control and Prevention says heat is the most dangerous weather-killer in the United States in most years, leading to an average of 600 deaths annually.