1. A statement meaning that the weather is nice enough to have the top of a convertible car down.
2. a statement that is obviously intended as being humorous, but sometimes stupid blonde bitches like to take it seriously and use it as a means to stupidly make fun of their ex-boyfriends.
(if someone says "it's top-down weather" when it's lightly snowing.... obviously they are joking...)
boyfriend: It's Top down weather.
girlfriend: Uh.... no it's not.
boyfriend: Obviously it isn't. Are you dumb?