The problem is that it dosent get cool, even at night. Its Hot and sticky. ITs very uncomfortable to sleep in. It is really hard to imagine how miserably hot it is, but I promise you it is. You can thank us all later.
If you MUST go tent camping in June, I'd suggest running a portable AC unit/fan to your tent and setting it up at the zipper door, with an extension cord. We did this with a portable heater in in the winter time.
Stay cool!