UK weather: What's caused lightning and hail?

From strange-looking clouds, to very loud thunder, lightning and even hail - why is the weather in the UK so weird at the moment?

BBC weatherman Simon King explains why it can go from being really sunny to then really rainy.

It's all to do with warm humid air causing lots of moisture in the atmosphere.

And, Simon says there is more heavy rain on the way for certain parts of the country.

Take a look.