June is notorious for swarms! As long as I know my queen is healthy (plenty of eggs, larva, and pupa in large oval patterns in the center of several frames per hive box) I scrape out any swarm cells.
After visiting several student hives this past week, I have found anywhere from two to several swarm cells per hive. If you check your colony every 12 days and do this simple task of ridding your colony of swarm cells, you should have a great season! When a swarm cell is allowed to fully develop, the queen that chews her way out of that cell tends to fly out of the hive which entices 30-70% of the colony to follow her to a new home. If she is found by the existing queen before escaping the hive, they will fight, which can cause damage and death to one or possibly even both queens. For those of you who still find more than four frames with no wax drawn-out yet, you need to keep feeding sugar water as this allows the bees to build much faster than having to obtain all the building resources from foraging flights.