I think if your application is complete in July, you will receive interview invites in August and get a decent number of pre-December interviews. It might differ depending on where your schools are, since I know some Southern/Midwestern schools have an earlier timeline.
I personally applied to mostly schools in the Northeast, and my application was complete on August 1 (I was only waiting on my committee letter to be sent, everything else I had filled out first week of June). I started getting interview invites the next day all the way until middle of November. However, the time range that schools want you to schedule your interview varies- for example, one school invited me in August but the dates they gave me to choose from were in October, and another school called me to interview in November and had availability 4 days later. My earliest interview was the first week of September and I interviewed all the way until late November. I had two interviews scheduled for December which I cancelled, but interviews go on until April/May or until the class is filled. That being said, I don't think you'll have trouble missing summer classes 🙂 Hope that helps!
