Daly City police Sgt. David Mackriss said the woman was trying to cross East Market Street at First Avenue during heavy rain just before 5 a.m. when a passing vehicle hit her.
"It appears that she was not in a crosswalk," Mackriss said.
Mackriss said the male driver stopped and tried to help her, and called 911.
The woman, identified as Lolita Estacio, was taken to San Francisco General Hospital, where she died at about 5:30 p.m., according to the San Francisco medical examiner's office.