US braces for second day of scorching weekend temperatures

Americans braced for a second -- and equally scorching -- day of dangerously hot weather Sunday, with daytime temperatures forecast to approach 100 degrees Fahrenheit (38 degrees Celsius) across a number of major US cities.

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

"The temperatures we're seeing in our city today and tomorrow could be the highest we've seen in years. Take it seriously," New York Mayor Bill de Blasio said on Twitter.

The heat was expected to continue through late Sunday as a high-pressure system off the Atlantic coast ushered in steamy, subtropical air.

"Dangerously hot conditions will continue through Sunday," the National Weather Service (NWS) warned for the Washington and Baltimore area, where forecasters predicted high temperatures ranging from 95 to 100 degrees for a second day.

"High temperatures and humidity could quickly cause heat stress or heat stroke if precautions are not taken," the NWS added.

People were urged to stay hydrated, watch out for the sick and 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.

In Arkansas, 32-year-old former NFL player Mitch Petrus died of heatstroke Thursday after working outside his family's shop.

Heat warnings have also been issued for parts of eastern Canada. In New York, 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. Meanwhile the two-day OZY Fest -- a food, comedy and music festival set for Central Park -- was also called off.

In Washington, a popular weekly outdoor summer jazz concert at the National Gallery of Art Sculpture Garden was cancelled.

New York City opened 500 cooling centers for residents.

At least three public defenders said on Twitter that inmates in New York's notorious Rikers Island jail complex were suffering with no air conditioning, and that some guards had turned off fans as punishment, resulting in "deadly conditions."