Dangerous heatwave scorches US ahead of Fourth of July holiday

Record-shattering heat wave tests power grids and holiday plans across East Coast

President Donald Trump and the White House were already facing blowback from families over a fireworks display that is not due to begin until 10.30pm on Saturday night (Washington time) and could start as late as 11pm.

Local officials are responding by opening cooling centers, adjusting public events and expanding emergency services as crowds gather for fireworks, festivals and Independence Day celebrations.

Temperatures in the high 90s Fahrenheit (30 degrees Celsius) were forecast for the Northeast; Philadelphia and Boston could top 100.