The tour group isn't affiliated with the Cannabis Cup, sponsored by High Times Magazine, which has run similar events for medical marijuana in nine cities. The magazine's editorial director, Dan Skye, says this month's U.S. Cannabis Cup was timed for the April 20 weekend.
"4/20 is the national stoner holiday, for lack of a better word," Skye said. "It gets bigger every year, and this year, after the legalization votes, it's going to be absolutely huge."
The magazine planned to award Snoop Lion with a "lifetime achievement" award at a Denver ceremony Friday. A Cypress Hill/Slightly Stoopid concert was planned Saturday at the iconic Red Rocks Amphitheater just west of Denver. Both events sold out weeks ago.
A few dozen miles northwest of Denver, the University of Colorado in Boulder will try to dampen pot celebrations on April 20. The campus once held the nation's largest college 4/20 celebration, drawing an estimated 10,000 in 2010. The legendary smokeout was cited by Playboy magazine when it named Colorado the nation's top party school in 2011 .
After the Playboy mention, the university stepped up efforts to shut the celebration down. Campus officials last year roped off the site of the smokeout, Norlin Quadrangle, reducing the 4/20 crowd to a few hundred protesters. The school planned another shutdown Saturday.
Celebrations were planned in Washington state, too, though April 20 isn't as broadly celebrated as Seattle's annual Hempfest, which draws hundreds of thousands of people to a waterfront park every summer.
The April 20 celebrations in Washington included a Seattle party being put on by DOPE Magazine at an artist work space and studio. About 1,500 were expected for glassblowing demonstrations, music, dancing and a bar where revelers can vaporize their pot, plus the judging for the "DOPE Cup" - an award for the best bud. There will be a smoking tent set up outside, along with food trucks to combat any cases of the munchies.
"It's pretty monumental," said DOPE editor in chief James Zachodni. "This is the first time in the U.S. there's been a cannabis holiday with a legal aspect to it."
Back in Colorado, longtime pot user Andrew Poarch says this year's April 20 observations in Colorado have taken on epic significance. He's joining dozens of friends to hire a bus from Colorado Springs to attend Denver's Cannabis Cup.
"It's going to be a lot bigger, a lot more people," he predicted. "People are trying to outdo themselves because it's a party and a celebration. We beat prohibition. It's a pretty big deal."