Really depends on where you work. Most companies offer vacation time (that can be taken any time of year, not just in the summer) based on length of service, and it varies anywhere from 1 week to 3 or more the longer you are with a company.
If you are working for a school system, you might have "summer vacation" when school is not in session for the summer, but that also varies, depending on the position. You would need to check with the human resource department for the district you are considering. Generally though it's about a month or so (depending on if it's a 10 or 11 month position).