Nearly 150m people sweltering through deadly US heat wave

The United States was sweating through a weekend of dangerously hot weather, with major cities including New York, Philadelphia and Washington experiencing temperatures approaching 100 degrees Fahrenheit (38 degrees Celsius).

An oppressive heat wave stretching from the Midwestern plains to the Atlantic coast had nearly 150 million people struggling to stay cool amid scorching temperatures.

Heat index values -- combining the effect of heat and humidity -- could reach 110 to 115 degrees, particularly in the east, the National Weather Service (NWS) said.

Children cool off in water fountains at Herbert Von King Park.

Waves of heat

It warned that "dangerously high temperatures and humidity could quickly cause heat stress or heat stroke if precautions are not taken."

People were being urged to stay hydrated, watch out for the sick and the elderly, stay inside as much as possible and not leave children or animals in cars.

The heat wave already claimed at least three lives, including two earlier in the week in the eastern state of Maryland.

People visit the beach in Ocean Grove, New Jersey. 

Heat warnings

Heat warnings have also been issued for parts of eastern Canada.

In New York, Mayor Bill de Blasio declared a heat emergency.

The New York City Triathlon, which had been scheduled for Sunday, was cancelled for the first time since its founding in 2001.

The estimated 4,000 participants, many of whom had traveled long distances to race, will receive full refunds of entry fees of up to $399, organizers said.

A child cools off in a water feature at a park in the Shaw neighbourhood.

'Serious, serious stuff'

New York City opened 500 cooling centers for residents.

"Saturday is going to be really, really bad, on through Sunday," de Blasio said in a warning to the city. "This is serious, serious stuff."

Climate data showed June was the hottest month on record worldwide, with a heat wave across Europe smashing national records.

Agence France-Presse