PS. It's not really possible to answer your question without having more info. Depending on weather,settings,and shot details, it could be a lot of different things that could cause what you've described. Where I live it gets hot and humid this time of year, and air conditioning can cool your lens to the point that it will attract moisture when you take it outside.
Sorry for the necro.....something odd happened and my post never went to the Goblin Valley thread and instead it quoted a post in this thread and replied here.