People across the world have been experiencing some very weird weather recently. In Moscow in Russia, the city has sizzled in a sweltering heat wave.
The heat has caused forest fires and dense smog - even dogs have been affected! Weather forecasters think it's due to changes in something called the jet stream.
The jet stream is a current of warm air high up in the atmosphere. It normally flows in a wavy pattern from west to east. But this summer it's a really weird shape!
This is causing extreme weather in the countries stuck under the jet stream - like Russia and Pakistan.
In Pakistan the motionless jet stream has meant the monsoon season has been worse than ever, causing terrible flooding.
This is because during the rainy season the land heats up, and the warm air above it rises. When this happens colder damp air from the sea sweeps inland to take its place.
The hot air above Pakistan is swirling about very quickly because of the jet stream - so more wet air is being sucked in from the ocean.
All this cold wet air drifting across the land means there are bigger clouds, and more rain! No one is quite sure why the jet stream has changed shape this summer.
And in China, all that cool damp air has caused heavy rain that has led to terrible landslides.