Someone who’s always daydreaming or talking about wild, impractical ideas may be spending too much time in cloudland — a mental dreamland or state ruled by imagination and unreality.
If you say that someone always "has their head in the clouds," it means that they're absent-mindedly dreamy and impractical, guided by whimsy. You could say that they're living in cloudland. The term is also used to describe the sky, where clouds wander by aimlessly, seemingly free from the cares and concerns that people face down on the ground. So if you’re spending a lot of time gazing up at the sky and wondering if it's really possible for pigs to fly (instead of doing your math homework), it’s probably time to get out of cloudland.