What's causing the UK's heatwave?

This video is from July 2015.

The UK is preparing for a predicted heatwave this week.

Forecasters have said that Wednesday could not only be the hottest day of this year but the hottest day since July 2006.

According to the Met Office, we could see temperatures of up to 35 degrees Celsius.

Health experts say the heat could be dangerous for older people, young children and those with serious illnesses.

BBC weatherman Simon King came into the studio to tell us about the scorching heat.