"Let me be clear, as clear as I can be: It's not good," she said. "Our dangerous winter has arrived."
RELATED: San Francisco Mayor London Breed attended French Laundry birthday dinner 1 day after Gov. Gavin Newsom
The city is preparing to announce new restrictions this week as the virus spreads rampantly. However, a news conference set for Wednesday afternoon was canceled.
The number of positive COVID-19 cases has tripled in the past three weeks, said Health Director Dr. Grant Colfax. COVID-19-related hospitalizations have doubled in 10 days.
"On Oct. 22 in San Francisco we had an average of 34 new cases per day," said Colfax. "Now, San Francisco has an average of 140 new cases per day."
Colfax said that if current trends continue, the city will see a shortage of hospital beds around Christmas.
"We literally have little time to spare," the health director warned.
On Saturday, the city entered the state's purple tier, prompting more indoor business closures and a new nightly curfew. However, both Breed and Colfax said even more restrictions are on the way.
"We are going to have to take more restrictive action, and it pains me to say that," the mayor said.
MAP: CA counties that can, can't reopen under new rules
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Breed said the city was looking to nearby Santa Clara County as an example for what further restrictions might be needed. Santa Clara recently announced a mandatory 14-day quarantine for those traveling into the area from 150 miles or farther. Santa Clara has also moved to limit social gatherings and further reduce capacity at businesses.
Closing outdoor dining entirely, as was done recently in Los Angeles County, is also on the table, she said.
"We are in trouble and we are sounding the alarm, so that's going to mean some real challenging months ahead."
More reopening rollbacks and/or restrictions are expected to be announced as earlier as Wednesday, Breed and Colfax said.
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