Does your gym get too crowded for you in the summer? Try a college's gym! Most students clear out during the summer leaving the gyms quite empty. In general: by taking 1 class during the summer you have access all summer included in your tuition. Some colleges allow students who took spring and/or are registered for fall to use the facilities during summer at no extra charge. If you're not a student, many offer community memberships semester to year lengths and are comparable or less than a gym
From what I've seen, many people using the gym in the summer are professors and staff, so it's not just the kids working out! If you have a community college close, you'll likely see people from all walks of life.