Tens of thousands of people have held mass rallies and other events in cities across the US as part of a worldwide demonstration known as the Rise for Climate.
The protesters on Saturday demanded that officials speed up transition to a world powered by renewable energy rather than planet-warming fossil fuels, and protect the people most susceptible to climate-addled weather, including droughts, heatwaves and superstorms.
The protests peaked in San Francisco as around 30,000 people took part in marches, calling on California Governor Jerry Brown to end fossil fuel extraction in the state, organizers said.
The march came just days before the opening of the Global Climate Action Summit in San Francisco, where officials and business leaders from across the world will discuss accelerating climate programs.
Brown has come under criticism for allowing the expansion of natural gas and oil extraction under his watch.