The watcher

You may not know who I am but, let me tell you this:
I'm always watching, even in the worst of weather. You must be wondering where it is that I hide so you don't see me but, that's the thing; I don't hide. I don't have to. I'm invisible to the naked eye and if you get close, you can only see yourself. How many times have you seen me? Probably tons of times but u never cared to take an extra look. You, like all people pass over me and let me follow you around. I even know who you are. If you dare to read outside, I'm there already. Watching from under that big tree in the park. I know it sounds weird, the way I'm explaining it all but, if I don't riddle my occupation to you, what fun is that?