What's the nuance of "the idea" here? Would "I've always loved summer and Sun" without "the idea" make the same sentence?
To have an "idea of something" means that you like the thought of it, but often you have never experienced it yourself. In this case, Olaf likes "the idea" of summer and sun, but he doesn't know if he actually likes it because he has never experienced it since he would melt. So to have an "idea" something usually means you are imagining what something would be like that you have never before seen or done. Ex: I love the idea of owning a dog, but they are too expensive. Ex: I like the idea of playing in the snow but I've never seen snow!