This list may help you somehow: Barbecues, picnics, swimming, a suntan, flying, exotic holidays, change of pace of life, catching up with reading, chic fashion, getting away from it all, sports, getting fit, the beach, mountains, no work, meeting up with friends, camp, family life, adventure sports, meeting new people, life outdoors, lots of sleep.
Before you get together to discuss the topic with your friends, you may like to visit this The New York Times page to view the way New Yorkers enjoy summer. Some of the summer rituals come together with audio, so that will give you the opportunity to listen as well as reading.