You never know when it will turn foggy in Golden Gate Park except on April 20.
Some 20,000 people packed Hippie Hill for the annual celebration.
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"At 4/20 when everyone smoked at the same time it was like the sky turned blue and then grey and then blue again. It was beautiful," said Mike Schwartz of greenRush. "I'm from Canada and I flew down here today just for this and man, San Francisco really knows how to smoke."
This is the first gathering since recreational use was legalized.
"This is our first time here," said Walnut Creek resident Kristin. "We're just here for the good vibes and the nice weather...day in the city."
A fence wrapped the meadow for the sponsored event that's still not sanctioned by the City of San Francisco.
"No arrests to speak of," said SFPD Public Information Officer Robert Rueca. "We did issue a number of citations beyond the park."
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In short succession around 3:30, San Francisco fire and paramedics responded to soberingly serious medical calls.
"We found at least two or three that were not breathing when our personnel arrived," said San Francisco Fire Department Battalion Chief Brook Baker.
Paramedics used the anti-overdose medication, Narcan, on several people. A dozen were transported to nearby hospitals. Four people declined medical care.
The SFPD is investigating the possibility that people ingested the narcotic fentanyl.
In years passed, there's been up to five tons of garbage removed from Golden Gate Park following the 420 celebration, but this year event sponsors are helping to fund the cleanup.
Organizers cleared the meadow by 5:30 p.m.
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