In March, just days after San Francisco issued its shelter-in-place order for COVID-19, 420 Hippie Hill officially canceled its annual event for cannabis enthusiasts in Golden Gate Park. 

But with the city's parks still open for public recreation, the city is concerned that 4/20 may return to its renegade roots, with smokers unofficially congregating in Robin Williams Meadow come Monday.

For decades, the annual marijuana bonanza has drawn tens of thousands of people with the city's tacit consent. But this year, officials are drawing a line in the sand.

In a press briefing this week, Mayor London Breed — who, as District 5 Supervisor, worked to make 4/20 a semi-official, semi-city sanctioned event — issued a clear warning.

"We will not tolerate anyone coming out to San Francisco for 4/20 this year," Breed said. "We have been very welcoming ... but this year we will be very strict with our policies. We will be prepared if people show up."

The city plans to erect a perimeter fence, closing all access to Robin Williams Meadow and Hippie Hill. Unspecified roadblocks and traffic diversions will be in place to prevent floods of vehicular traffic into the area. And a bolstered police force will be patrolling the park.

"We will cite and, if necessary, arrest," Breed said. "Do not come to San Francisco on 4/20."

For those planning to honor the occasion at home, this will be the first 4/20 that the Upper Haight has had a legal source for buying marijuana: Berner's on Haight, which opened last December. 

Cannabis retailers are considered an essential business under the shelter-in-place. In a statement, Berner's said it would encourage patrons to order ahead for home delivery, and host a virtual celebration online.