A bitterly cold airstream from the North Pole has produced these amazing Cumulo-Nimbus clouds over Yorkshire and Lincolnshire. They are formed as air currents rise and the water vapour in the atmosphere condenses into water droplets and ice crystals. These clouds rise up as high as the troposphere where they spread out like a blacksmith's anvil or a mushroom.
These clouds can produce hail, sleet and snow showers which can dramatically reduce visibility. Because they contain ice, they are capable of producing thunder and lightning at the same time as snow; thunder-snow.