I got the following from answers.com:

White dinner jackets are common in warm climates, and in the summer in some temperate countries. The British Isles are not considered warm enough for white dinner jackets to be acceptable, even in the summer. In the United States and Canada white dinner jackets may be worn from mid-April through to Labor Day. The wearing of white dinner jackets in Europe and temperate climates is frowned upon in the United Kingdom; and many maintain they are appropriate only in India, the Caribbean, and in the former south east Asian colonies.


So I guess it depends oh when you are going and where...