This week brought the first test of the year for millions of Americans in the south-west who routinely see high heat come summer.

Temperatures on Thursday were expected to hit as high as 112F (44C) in parts of Nevada, Texas and California, reaching 121F in California's scorching Death Valley.

As Trump took the stage just after 17:00 EST (22:00 GMT) in Phoenix, the temperature was 111F.

Trump fans began lining up for the event early on Thursday morning, in what was the first rally for the former president since his criminal conviction in a New York hush-money case.

There were several thousand people queuing outside the massive Phoenix Dream City Church to see Trump speak on Thursday.

Strict security measures meant it took time to get everyone inside the mega-church.

As supporters waited outside the campaign rally, BBC News saw several people being treated for heat-related issues and two were taken to hospital.

Eleven attendees in total were taken to hospital with heat-related symptoms, according to Phoenix Fire officials.

Firefighters were seen using ice to treat others and cool them down.

On Thursday - two weeks before summer even officially starts - the National Weather Service (NWS) forecast record-breaking temperatures in interior California, and parts of Nevada and Arizona.

In Phoenix, an excessive heat warning is in place through Friday, with people being asked to limit time outdoors and stay hydrated.

Trump started a small campaign tour with the stop in Phoenix on Thursday, exactly a week after he was found guilty in New York.

The former president spoke for about 90 minutes before departing for a fundraiser in San Francisco. He is next expected to hold a campaign event in Las Vegas on Sunday.

That city is also seeing record temperatures. The forecast high of 112F in Las Vegas on Thursday would be the city's earliest observed 112F day on record.

Temperatures are 20 to 30 degrees Fahrenheit above average for this time of year, according to the NWS, though they will cool slightly by the time Trump visits on Sunday.

The intense heat has placed more than 30 million people across the south-west region under alerts for dangerously hot temperatures, with officials asking residents to take precautions.

Heat-related illness and even death are becoming more common in Phoenix and the American south-west.

While heat domes were once described as rare, heatwaves and heat domes are becoming more common and intense because of human-induced climate change, scientists say.

The world hit 12 straight months of record-high temperatures, the European Union's Copernicus Climate Change Service said earlier this week.

Last month was the hottest recorded May in history.