Forecasters warn of record-breaking US summer heat amid intense El Niño

More than 100 million people could be affected in week leading to 4 July, with increased risks of droughts and wildfires

Meteorologists are anticipating a tumultuous summer that could rank as one of the US's hottest ever.

New data released on Tuesday showed the first six months of the year were the hottest ever measured for parts of eight western states.