The cream or white dinner jacket is a tricky item to negotiate. Somehow, it doesn’t seem quite so formal as the standard black or navy, and it brings with it a whole host of sartorial issues that you simply don’t get with the darker jacket.
This all begs the question; when is it appropriate to wear one? I have a book at home that states you should only wear a cream dinner jacket when on a cruise, and even then only after you have reached Port Said.
However, that book was written in 1936, so perhaps you should take it with a pinch of salt.
I think generally, at an outdoor event in the summer would be the perfect time to wear a lighter dinner jacket.