Getty Images Copyright: Getty Images Chicago's frozen shoreline Image caption: Chicago's frozen shoreline

At least 21 people have died in one of the worst cold snaps to hit the US Midwest in decades.

Ninety million people - a third of the US - have seen temperatures of -17C (0F) or below. Some 250 million Americans overall have experienced the "polar vortex" conditions.

Read more here.

And in the UK, travel by road, rail and air has been disrupted by snow and ice, with weather warnings issued for Friday and overnight.

The Met Office yellow warnings for snow and ice cover several areas of the UK, while a separate warning for ice is in place for southern England.

There's more on that here.