Mayor London Breed says Robin Williams Meadow will be fenced off.
RELATED: Bay Area rapper E-40 talks with ABC7, urges people to stay inside on 4/20 to prevent spread of COVID-19
She urged people not to come to San Francisco to celebrate.
"We will patrol the area," said Mayor Breed. "We will be on the lookout for large massive events in our city, because the bigger issue for us, is that the last thing we want to see, is San Francisco go backwards."
RELATED: Thousands gather for 4/20 at San Francisco's Golden Gate Park
Breed says she's hopeful that people will abide by the order, like they did last year.
WATCH: Split-screen video shows Hippie Hill on 4/20 in 2020 versus 2018
Coronavirus Impact: Split-screen video shows Hippie Hill on 4/20 this year verse 2018
Organizers say while the event celebrating all things cannabis is canceled in person, it's not canceled in spirit.
A number of virtual events are being planned.
RELATED: How April 20 became a pot day
See more stories and videos about 420 and cannabis here.
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