Police are bracing for thousands of revelers to celebrate 4/20 in San Francisco.
Pot smoke is expected to fill the air in the Haight-Ashbury district and at Golden Gate Park's Hippie Hill.
Police during last year's celebration made several arrests after someone fired a gun in the crowd. No injuries were reported in the shooting.
The San Francisco Police Department said officers will be out in full force Monday.
"It's basically an unpermitted unsanctioned event," San Francisco Supervisor London Breed said.
Breed said the 4/20 party also creates safety and traffic concerns. This year's event is expected to snarl the Monday evening commute.
Retailers on Haight Street are ready, with some selling souvenirs. Other shops are preparing to to close early.
