Nasa has used data to construct an air temperature map of current atmospheric conditions

Air temperature at 2 metres

40C>

<-40C

-20

0

20

1

The polar vortex is an area of low pressure and extremely cold air that swirls over the Arctic

2

Disturbances in the jet-stream and the intrusion of warmer air can disturb this polar vortex sending Arctic air south into middle latitudes

Extremely

cold air

masses

plunge

south

Warmer

than usual

air over

Arctic

3

Masses of extremely cold air have plunged towards the interior of North America and at least 90 million Americans could experience temperatures at or below zero (-18C)

<-40C

-20

0

20

40C>

Air temperature at 2 metres

1

The polar vortex is an area of low pressure and extremely cold air that swirls over the Arctic

2

Disturbances in the jet-stream and the intrusion of warmer air can disturb this polar vortex sending Arctic air south into middle latitudes

Warmer than

usual air

over Arctic

Extremely cold

air masses

plunge south

3

Masses of extremely

cold air have plunged towards the interior of North America and at least 90 million Americans could experience temperatures at or below zero (-18C)