People in Arizona are posting pictures of the things they claim have melted in the extreme heatwave, which has seen temperatures soar to 120F (48.8C).

Images of wilting catci, a buckled postbox, a credit card curled out of shape because of the heat and a biscuit that was cooked on a car's dashboard have all appeared on social media.

A video of an egg being fried on the ground has also appeared, while one Twitter user showed himself wearing oven gloves to drive, because of the temperature inside his car.

Another motorist stopped at an intersection in Phoenix showed the local temperature was 122F.

So high are the temperatures that people have burned their bare feet on pavements and planes to be grounded.

The extreme heat has swept across parts of Arizona, Nevada and California, causing a water shortage in one area. The risk of wildfires has also increased because of the heat.

American Airlines cancelled 50 flights in and out of Phoenix last week as smaller regional planes have a maximum operating temperature of 118 degrees Fahrenheit, The Washington Post reported.

In Phoenix, the main burn centre has treated people with burned feet from walking outside with no shoes on or contact burns from touching hot car interiors.

Arizona Burn Centre director Dr Foster told the Associated Press that this June was the worst the centre has seen in 18 years.

The centre’s emergency department usually treats between 10 and 15 people a day, but this number has jumped to up to 30 people a day in the heat wave.

Dr Foster said one child received contact burns after crawling through a doggy door onto the hot pavement.

“Getting up to 120 really makes a difference,” he said.