[momoreg]

Fondant takes some time to learn, so practice as much as you need to, so you're not cursing, trying to get it to work at the last minute. I wonder what you are planning to use under the fondant, if not buttercream...?

Fondant does no better or worse in summer weather than buttercream. I typically have buttercream under the fondant for a smooth look, but I've heard of people using jam or royal icing underneath it as well. The truth is, humidity will affect almost any finish, if the contents of the cake are cold, and the surrounding air is hot.

To obtain a nice creamsicle flavor, you really need dairy, but maybe you'd consider an orange curd or marmalade as your filling, for an orange (but not creamsicle) flavor.