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 U.S. 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.

Heat warnings have also been issued for parts of eastern Canada. In New York City, Mayor de Blasio declared a heat emergency. The New York City Triathlon, which had been scheduled for yesterday, 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 prison complex were suffering with no air conditioning, and that some guards had turned off fans as punishment, resulting in "deadly conditions." The Brooklyn Defender Services legal aid group said some inmates didn't have summer clothing, only long underwear provided by the group last winter.

Last week, the National Weather Service office in the midwestern city of Omaha baked a tray of biscuits, savory breakfast bread similar to scones, on the dashboard of a parked car. After nearly eight hours and with temperatures on the pan reaching 185 degrees, the pastries were almost fully cooked. Climate data showed June was the hottest month on record worldwide, with a heat wave across Europe smashing national records.