If you are a summer camp marketer using emails to market your camp to parents, Tuesday through Thursday mornings are generally the best time to send them. If your emails are directed at kids, sending them in the late afternoon when they get home from school is the best time. (And you better be sure you’re complying with the coppa law, too.)
If you are using emails to send camp newsletters, frequency and timeliness are important. Since your recipients are expecting to receive your newsletter on a regular basis, so be certain to send your emails at the same time, every time.