Young people around the world are expected to strike on Friday (and again one week later) as part of the Global Climate Strike, bringing urgency to an issue that is likely to disproportionately affect younger generations who will live to see a world that could become increasingly uninhabitable.

In New York, the city’s 1.1 million public school students have been granted permission to take the day off and participate in the historic climate action. On September 12th, the school system vowed on Twitter to excuse the absences of students participating in the strike (if their parents allow it). But you do not need to be a student to join in the movement. Here’s how New Yorkers can take part in the protests, which are expected to occur in more than 150 countries (and in more than 800 locations in the U.S. alone).

At noon on Friday, activists will gather at Foley Square in Lower Manhattan. From there, the strikers will march to Battery Park. There, Greta Thunberg, the 16-year-old climate activist who arrived in New York last month after sailing across the Atlantic on a carbon-neutral yacht, is expected to speak to the crowd. So are several of the 21 young plaintiffs who filed a lawsuit against the U.S. government for failing to protect them from climate change.

Since her arrival, Thunberg has been helping to make Friday school walkouts a routine event, though none so far on the scale of tomorrow’s strike.

These protests are scheduled to occur ahead of the U.N. Climate Action Summit in New York, aiming to put pressure on the world leaders arriving in the city next week. The school walkout will reoccur after the summit on September 27th. “This is a global moment to show politicians everywhere that our movement is growing from strength to strength and we won’t stop until we get climate justice for everyone,” the organizers note on the Global Climate Strike website.

The site signals the urgency that is animating the movement: “Our house is on fire—let’s act like it.” Climate change could pose an existential threat to civilization by 2050.