@FiddlerDog There are several levels of tourneys during the summer that can be played by juniors, collegians, young pros, and adults. In descending/overlapping level of ability, there are the pro Challenger and Future tourneys (and qualifiers), UTR's own PTT tours (often ATP ranked players play these for the prize $), WC tourneys to get into the 1st two, men's prize money opens (could be hosted by UTR or USTA or other nonsanctioned) and ITA summer circuit events (put on by college ITA organization but anybody over 13 who pays $30 membership fee can play). Former junior players who dont play college tennis or pro tennis can play the open and ITA circuit events-unlikely they would get in the higher two events unless they won a WC tourney first.
One note though-not all tourneys are weekend tourneys-the ITA summer circuit are usually Fri-Monday but many other tourneys including high level USTA juniors and ITF juniors run during the week. In the summer the high level tourneys can take a week or more.