London is the capital and most populous city of England and the United Kingdom. It is a leading global city in the education, arts, commerce, finance, healthcare, entertainment, research and development, fashion, media, professional services, tourism and transportation. It is the world's most-visited city as estimated by international arrivals and has the world’s largest city airport system measured by passenger traffic. London's universities form the largest concentration of higher education institutes in Europe. London has a temperate oceanic climate, with warm summers and cool but not cold winters. During October, London will have a fairly cool temperature.