MARK AUSTIN THOMAS: Happy solstice! That's right, today is the first day of summer and you know what that means: It's time for summer camp for lots of kids. Rachel Dornhelm tells us camps are now a booming business.

RACHEL DORNHELM: Think of summer camp and you might imagine skits or singalongs. But probably not $20 billion in revenue.

This steadily growing industry now boasts 12,000 camps around the US. The biggest jump has been in day camps, with enrollments up more than 20 percent in the last five years.

Marla Coleman, with the American Camp Association says camps are finding the big draws now are new adventure specialties, like mountain biking or caving.

MARLA COLEMAN:"The other interesting program additions are around mind and body activities such as yoga."

Companies running multi-site camps are also gaining a foothold. They can build brand identity with families. And buy everything from marshmallows to art supplies in bulk to make their financial load lighter.

I'm Rachel Dornhelm for Marketplace.