What extreme heat does to the human body

The US National Weather Service says nearly one half of the population of the United States is under an active heat warning. The west of the country is experiencing record temperatures - with Las Vegas at almost 49 degrees Celsius this week. And it's been a similar story elsewhere in the world, where experts say climate change is causing heat waves to grow more frequent on practically every continent. The World Health Organization has found that extreme temperatures cause more deaths worldwide than any other weather-related factor. So with more and more people all over the globe being exposed to sustained heat - we take a closer look at the risks. For more on this, we talk to our science correspondent Derrick Williams.