Bored? Yes, sometimes.
On a regular basis? You're either not being challenged, or it could be some clinical depression- which is NOT "feeling sad", but a physical problem with your serotonin uptake cycle.
If you're used to a school year routine, it's normal to not know what to do and become bored. That;'s especially true when people spend too much time on the internet involved in activities they aren't driving themselves. Find a program of activities for the summer- something really productive, like volunteering or better yet, a job. And be conscious about what *interests* you. Getting involved in something that interests you will pay off for life. You're old enough to think about that, and have an active part.