Heat dome bakes California and US South-west

Weather warnings issued for areas affecting up to 35 million people as temperatures rise

A sign board warning of extreme heat in Death Valley, California. Reuters

A heat dome that has settled over Mexico and parts of the southern US is spreading west and north, with record-breaking temperatures expected.

Thursday was expected to be particularly hot for millions of people and the temperatures will be dangerous for vulnerable populations and those exposed to the elements who are unable to cool off.

About 35 million people will be under heat warnings announced for much of the south-western region throughout the weekend, including Tucson and Phoenix in Arizona, and Las Vegas, Nevada, as well as Palm Springs, California, with temperatures in some areas to pass 46°C.

Temperatures in Texas breached 43°C this week as the heat dome moved north-west, with extreme heat warnings announced for much of California.

Death Valley in California was projected to hit 49°C.

The heatwave comes after UN Secretary General Antonio Guterres said humankind is on a fast track to “climate hell”, after scientists announced the world experienced its hottest May on record and the 12th consecutive month of record heat.

“Extreme heat can be deadly,” Governor of California Gavin Newsom said.

“Together, let’s do everything we can to stay safe. The state is taking action to protect and inform communities and Californians should take steps now to protect themselves from the heat. Stay cool, stay hydrated and stay connected.”

In Phoenix – America's hottest big city – emergency responders are using new tactics in hope of saving more lives in a county where there were 645 heat-related deaths last year, according to the Associated Press.

Starting this season, the Phoenix Fire Department is immersing heatstroke victims in ice on the way to hospital.

“We’ve been seeing a severe uptick in the past three years in cases of severe heat illness,” said Paul Pugsley, medical director of emergency medicine with Valleywise Health.

Record highs of 43.3°C were forecast for Phoenix and Las Vegas on Thursday.

“There's a very high-pressure system over the South-west that's bringing the first heatwave of the summer to the region,” said Sean Benedict, a lead meteorologist with the National Weather Service based in Phoenix.

Using its Heat Risk sliding scale to measure potentially dangerous heat in a 24-hour period, the National Weather Service in Las Vegas forecast “extreme” heat in parts of southern Nevada from Wednesday throughout the weekend.

“Extreme” is the most dangerous heat level on the scale, and so rare that it occurs only a few times a year, the weather service said.

It warned of little to no relief overnight from daytime heat.

Cities across the region have adopted measures to help residents deal with the heat, including setting up cooling centres and sprinkler systems, as well as ensuring city employees receive cool water, shade and extra breaks at their workplaces.