Normally the jet stream is a giant loop of high speed winds that whip round the upper atmosphere, writes science correspondent Tom Clarke.

The jet stream isn't involved in day to day weather - it's too high up - but because it pushes the atmosphere around it's very important in steering large scale weather patterns below. [...]

The stream has split in two. One arm has gone north, another south. The patch in the middle is Russia's drought. A circulating pattern of air has been sitting over Russia for far longer than normal, causing the extreme temperatures and wildfires they've had there.

But what's happening over Pakistan is even stranger. The southern arm of the Jet stream has looped down so far it has crossed over the Himalayas into north western Pakistan. Experts at the Met Office tell me this is very unusual.

And the result is that the fast moving jets stream winds high up has helped suck the warm, wet, monsoon air even faster and higher into the atmosphere - and that has caused rains like no-one can remember. It has turbo charged the monsoon if you like. They're not sure that's ever happened before.