A widespread, stubborn and likely record-breaking heatwave is set to blanket much of the U.S - thanks to a 'heat dome'.

It comes as dozens of environmental, health and labour groups - including the largest federation of unions in the U.S - petition the Federation Emergency Management Agency to recognise extreme heat as a natural disaster. 

• Guest: Jean Su, Energy Justice Director and senior attorney at the Center for Biological Diversity and lead author of the petition