London's weather is unpredictable. It can be cool, damp, and overcast, even in summer, but the odd summer day can be uncomfortably hot, as not many public venues, theaters, or the Tube are air-conditioned. In general, you'll need a heavy coat for winter and light clothes for summer, along with a lightweight coat or jacket. Always pack a small umbrella that you can easily carry around with you. Pack as you would for any American city: jackets and ties for expensive restaurants and nightspots, casual clothes elsewhere. Jeans are popular in London and are perfectly acceptable for sightseeing and informal dining. Sports jackets are popular with men. In five-star hotels, men can expect to be asked to wear a jacket and tie in the restaurant and bar, and women might feel out of place unless they're in smart clothes. Otherwise, for women, ordinary dress is acceptable just about everywhere.