The largest climate march in history is coming to New York City.

This event takes place on Sunday, September 21 to coincide with the United Nations’ Climate Summit happening later that week. The summit, at which recently designated UN Messenger of Peace Leonardo DiCaprio will address the UN, will gather global leaders from government, business, finance and civil society “to promote climate action for a healthy planet, sustainable economic growth and better standards of living for all.” Because these leaders are coming to UN Headquarters in New York, organizers of the People’s Climate March think it’s the perfect time to take to the streets.

“With our future on the line and the whole world watching, we’ll take a stand to bend the course of history,” explains the march’s website. “We’ll take to the streets to demand the world we know is within our reach: a world with an economy that works for people and the planet; a world safe from the ravages of climate change; a world with good jobs, clean air and water, and healthy communities.”

This mass effort to “peacefully flood the streets in historic numbers” to communicate the urgency for bringing about environmental change is being organized by more than 1,000 different environmental groups, businesses, religious organizations and concerned citizens.

The People's Climate March begins at 11:30 a.m. at Columbus Circle, and finishes at West 34th Street and 11th Avenue. The approximately two-mile march will conclude with a moment of silence, followed by a moment of alarm during which participants are asked to “make as much noise as you can when you hear 32 marching bands blowing their horns and church bells ring from around the city . . . sounding the climate alarm that has gone ignored for too long.”

The event’s full schedule of events can be found at Peoplesclimate.org.