Unfortunately, we usually have only 1 and a half summers off. In the one between 1st and 2nd year, people did a variety of things including research, preceptorship (working in a clinic or hospital), traveling, relaxing. This break is usually 2-3 months long. In the summer between 2nd and 3rd year (1-2 months) most people studied for the USMLE Step II for a chunk of it then relaxed the rest of the time. There is no summer vacation after third year, you work straight through.
At some schools, there isn't a summer break after second year either. You take a couple of weeks to study for Step 1 and then it's straight to 3rd year.
Must be nice to have that long off between 1st and 2nd year. My year ends in July and begins again in August next year.
