The city's previous record high temperature was 39.4 degrees Celsius, set in 2000, reports Xinhua news agency.
On Friday, the temperature in downtown San Francisco reached 41.1 degrees Celsius. On Saturday, it increased to 42.7 degrees Celsius, the US National Weather Service said.
"This was the highest reading since records were first kept there in 1874. That's the oldest climate station in California," a meteorologist said, adding "That's a significant record."
Forecasters said some inland cities in the San Francisco Bay Area, such as Livermore could reach 46.1 degrees Celsius, a temperature last recorded in 1950.
In Sacramento, temperatures reached 42.2 degrees Celsius on Friday.
Smoke from wildfires in Northern California and Oregon were blamed for the heatwave.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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