The term 'London Mists' refers to the frequent foggy weather in London, England. The four-letter crossword solution for this term is 'Fogs'. Fog is a type of cloud that forms close to the ground and is composed of tiny water droplets suspended in the air. It is often seen in London due to the city's high humidity and its location near the sea. The mists are a common sight in the city and can be seen throughout the year.