Brands hope to reach music festival fans this summer—way before they get to the campgrounds.

The prices of billboards on Interstate 10 heading toward Indio, California, home to the  Coachella Valley Music and Arts Festival, increased 31 percent in the four-week period from late March to early April, according to new research from OOH buying-and-selling platform AdQuick.

Coachella (April 12-14 and April 19-21) draws hundreds of thousands of people over two weekends.

AdQuick CEO Matt O'Connor says that billboard advertising along the routes to Coachella sold out in January. The cost: between $8,000 and $20,000 for each billboard over four weeks. O'Connor estimates that a few hundred thousand people will see each of those billboards in passing.

Outdoor advertising is growing, says O'Connor, and the popularity of billboards "is a pretty cool microcosm of the interest brands are having in outdoor advertising in general."

There's been particular interest from start-up apps and music agents hoping to connect with young fans, O'Connor says.

Highway billboards are just one way that brands are trying to reach fans outside the festival grounds. Marketers like McDonald's, Calvin Klein and American Express are hosting parties and other events at locations near Coachella. Attendees get free swag and custom photo backgrounds so that fans can share pictures on social media. 

Coachella marks the unofficial kickoff of the 2019 music festival season. Chicago's Lollapalooza is in May, followed by Governors Ball in New York City and Bonnaroo in Manchester, Tennessee.

"It's kind of known within the industry that everyone will come for billboards around Coachella time," O'Connor said. "Brands don’t realize they’re not the only ones trying to reach this unique segment at this unique place."

There's been particular interest from start-up apps and music agents hoping to connect with young fans. O'Connor said that the content of the billboards is largely targeted toward millennials who are likely to be at the festivals.

Highway billboards are just one way that brands are trying to reach fans outside the festival grounds. Brands like McDonald's, Calvin Klein and American Express are hosting parties and other events at locations near Coachella. Attendees get free swag and custom photo backgrounds so that fans can share pictures on social media. 

Coachella marks the unofficial kickoff of the 2019 music festival season. Chicago's Lollapalooza is in May, followed by Governors Ball in New York City and Bonnaroo in Manchester, Tennessee.