Heat dome's triple-digit temperatures fry US south-west

Firefighters are on standby to submerge heat-stroke victims in ice and some popular hiking trails have closed in Arizona as tens of millions of people across the south-western US swelter in record-breaking, triple-digit temperatures.

Two weeks before summer even officially starts, excessive heat warnings were in effect across parts of California, Nevada, Arizona and Texas. Forecasters see no relief for several more days.

Temperatures were predicted on Wednesday to reach 109F (42.7C) in Phoenix, 107F in Las Vegas, 110F in Palm Springs and 119F Death Valley, California.

By end of the day, the National Weather Service (NWS) says Americans in the region may experience "easily their hottest" weather since last September, according to the Associated Press.