The climate in UK is mild due to the influence of the Gulf Stream. The Gulf Stream is one of the strongest and most important ocean currents in the world.The Gulf Stream currents move warm water in the Atlantic Ocean from the Caribbean Sea northeast to northern Europe and the British Isles.The Gulf Stream brings warmth to the UK and north-west Europe and is the reason the UK has fairly mild winters.Without this steady stream of warmth, the British Isles winters are estimated to be more than 5C cooler, bringing the average December temperature in London to about 2C.