Rain is always expected in London, and often you will have some fog, but be ready for cold temperatures during the winter times. If you visit during the summer, you will have a great time in the many parks and you can enjoy (book in advance) a play by Shakespeare right at The Globe. While some museums are relatively empty and you can enjoy the art, others are crowded with thousands and thousands of tourists, especially in special occasions (right, Tate Modern!).
London is crowded and full of life every single day of the year.
