Environmental activists hula hooping in hemp skirts, men dressed in outlandish jump suits, families with small children and excited college students in tie-dyed shirts filled the National Mall Sunday.

They were there to see acts like the Flaming Lips, moe. and Los Lobos, as well as environmental activists and celebrity speakers, at the Green Apple Festival, an event designed to support sustainability efforts.

Kathleen Rogers, president of Earth Day Network, the organization that hosted the event, opened the festivities by encouraging everyone in the audience to work together to fight climate change.

Event producer Peter Shapiro said the event was important to help get the environmental message out, especially with this week’s Earth Day.

“This is one of those events that can’t change the world. But without them, the world can’t change,” he said.

Weather conditions remained overcast, but were still a big improvement from the downpour that rained out last year’s event.

Attendance was dismal at first, with only about 300 people crowding the stage, but as the day progressed, crowds grew in the thousands.

Lauren Winsten, a senior, said she came out to the Mall for not only the music but “to check out all the new green technologies,” which the environmental festival showcased.

“It’s great, while people are waiting between acts they can check out the booths and see what’s new and green,” she said.

For Miles Brundage, a junior, it was his second time attending the concert. Brundage said he came again for the free music and to support the environment, adding that this year’s concert was an improvement from last year.

Other students, though, showed up solely for the music.

“I don’t really think me being here is really doing anything for the movement,” said sophomore Matt Mersky.

Several celebrities, including Matthew Modine, Chevy Chase and Philippe Cousteau, took on activist roles to help spread the green message.

In an interview with The Hatchet, Modine discussed his global bicycle initiative, which encourages everyone to ride a bicycle for a day.

“We created a situation where we have to now work to solve these problems,” Modine said.

Philippe Cousteau, chief ocean correspondent for Animal Planet, championed the concert as “a way to send a little message about what we do to the environment”.

“We love the cause,” said Kev Marcus, violinist for musical group Black Violin. But he admitted that “the opportunity to perform with the Capitol as a backdrop” was a big incentive.

A few raindrops made an appearance as the Flaming Lips took the stage, but as the band’s lead singer Wayne Coyne made a brief crowd surfing attempt, the crowd didn’t seem to mind, as the band highlighted their performance by shooting streamers onto the Mall.