NICK HEXUM can hear the storms coming again. He is singer-guitarist with the band 311 and is calling from his island home in the Florida Keys, where he owns a six-acre plot of land about a mile off the southeast coast, a place he calls "this most beautiful island that I love with all my heart." And he remembers what happened in 2005.

That was a year of big destructive hurricanes, labeled with the otherwise innocent names of Wilma, Rita, Dennis and Katrina. Hexum's house was battered but survived, and he realizes that others obviously had it much, much worse. Thousands across the region lost homes, jobs, lives. The devastation led Hexum to delve into researching climatological issues and take up global warming as a cause.

"Hurricanes are going to get worse," Hexum says grimly. "We are on an upward trend of hurricane strength because we're on an upward trend of global temperatures. We really felt it hard-core last year."

That experience was enough to further inflame Hexum's existing environmental concerns. He bought a hybrid car (a 2007 Lexus), founded a nonprofit organization, LiberalHexum.org, and is having solar panels installed at his Laurel Canyon home.

This year, he raised $15,000 in pledges for LiberalHexum.org by running the Los Angeles Marathon (his first). He also has a solo project in the works, a collection of ancient pop standards ("Sweet Lorraine," "Smile," etc.), rendered as reggae songs, that he hopes can be used to raise more funds. Its working title: "Too Darn Hot."

"I love 311, but those things are very important," says Hexum, 36. "So I'm going to take a little time off and work on those other things."

That means an indefinite band hiatus will begin at the end of 311's current tour, which closes this weekend with shows at the Greek Theatre and the Santa Barbara Bowl. Hexum isn't sure how long it will last.

"I'm leaving it open-ended," he says, "because if there is any kind of deadline, that will ruin it."

The hiatus comes just as 311 is experiencing one of its most successful tours, playing bigger rooms and with more sell-out crowds than when 311 albums were going triple-platinum. Hexum can't explain the surge in numbers, but says many new fans seem to be in their late teens.