There are basically two reasons: (1) volunteer personnel and (2) weather. Regarding (1): for our events, we rely on the volunteer effort of many UCF undergrads and grad students. During the summer — which, by the way, for UCF, lasts from mid-May to mid-August — those students are often away from school. So we can’t be sure that we’d have enough people to actually hold an event. Regarding (2): summer is just often too cloudy, too rainy, too buggy, or too humid to have a pleasant outdoor nighttime experience. Also such conditions can be harsh on our telescope equipment. So it is best to assume that there will be no public or private events possible during the months of May, June, July, and August.
However if a particularly exciting astronomical event happens during the summer, we will try to have an event. In that case, we will announce it on our webpage and social media.