In the wake of a persistent heat wave, more than 85 million Americans are under excessive heat warnings or heat advisories, according to the US National Weather Service (NWS).

It said that numerous record highs were forecast to be tied or broken in the Northeast of the US, with heat index values up to 37.4 degrees Celsius in parts of Pennsylvania, Delaware, New Jersey and Oklahoma, Xinhua news agency.

On July 21, 73-year-old man from Allentown, Pennsylvania succumbed to excessive heat exposure, complicated by underlying medical conditions, according to local officials.

Meanwhile, a 66-year-old woman who had underlying health conditions died of heat also on July 22 in Dallas county, Texas.

It's estimated that hot temperatures in July have led to dozens of deaths including at least 17 fatalities from Maricopa county, Arizona.

The temperature also caused post-ponements or adjustments of sports events and delays of trains.

The Boston Triathlon, originally scheduled for Sunday, has been postponed to August 21 while participants competed in the New York City Triathlon with shortened courses on Sunday.

The US National Railroad Passenger Corporation issued multiple alerts from over the weeked on delays of its services in the Northeast due to heat-related speed restrictions.