As if to underscore the point of the Climate March, Washington, DC was muggy, sticky, and unseasonably hot. It was a perfect backdrop to the signs reading “Make the Earth cool again,” “It’s getting hot in here,” or “the Earth is melting.”

The People’s Climate March was rather cheery, as attempts to save the world go. When I arrived early, I was treated to a larger-than-life puppet show. Cardboard and papier-mâché pipelines — taller than the people holding them — spewed ominous gray clouds of CO2, methane, and “climate pollution.” Giant hands pushed them back — along with a massive, headless suit labeled “Big Oil.”

Though the march fell on the 100th day of Donald Trump’s presidency, it had been conceived long before the election. It was a successor of sorts to a 2014 march in New York City — where 400,000 people demanded action on climate change. Three years later, more than 200,000 people marched through the streets of DC, organizers said; an additional 370 satellite marches also happened worldwide.

The People’s Climate March was planned as a direct response to a distressing reality. There was 2016, the hottest year on record. It beat the previous record, set in 2015. The next hottest year after that was 2014. In fact, anyone who’s under the age of 31 has never experienced a colder-than-average month ever. Though climate change is often discussed as a future problem, it is, in fact, a current problem. High tides lap at Florida streets; Antarctica is splitting; allergies are getting worse; the Great Barrier Reef is hanging on by a thread.

The Trump administration has taken an aggressively denialist response. The Environmental Protection Agency is headed by Scott Pruitt, a climate change denier who has sued the EPA 14 times. There is the executive order allowing oil drilling in the Arctic; there is the executive order halting the Clean Power Plan, and undoing a temporary moratorium on new coal mine leasing on federal lands. There is, of course, the approval of the Dakota Access Pipeline’s last necessary permit. So despite the march’s original goals, many people view the climate march as a direct response to Trump’s policy. In fact, when Marine One flew over the rally gathered around the Washington Monument, hundreds of people flipped it off and yelled taunts.

Focusing too hard on the Trump administration in some ways misses the point, since most of the signs at the protest were about the bigger picture: higher temperatures, melting ice, rising oceans and — crucially — climate justice. Two previous marches, the Women’s March and the March for Science, struggled with inclusiveness, and were widely criticized for a lack of diversity. In contrast, the front of the People’s March was led by youth representatives of some of the communities hardest hit by climate change and environmental racism: Uprose, a Brooklyn-based group that helps retrofit communities likely to be hard-hit by climate change-related flooding (among its myriad other efforts); delegates of Sunrise Ceremony Native / Indigenous Women; and several organizations local to DC. They carried signs, danced, and yelled chants into megaphones at the top of their lungs.

But behind the line of marshals in bright pink shirts blocking traffic, emergency medical technicians on bikes pedaled in circles, ready to jump in and help anyone who collapsed as the temperature crept up. And for good reason: the sultry DC afternoon peaked at 91 degrees, breaking or tying all previous heat records for the day, which had been set in 1974.

Early in the march, one of the adult guardians of the kids leading the march turned around, showing off a nearly empty bottle of orange Powerade. “I’m almost out of fuel,” he told me, shaking his bottle tiredly. But he turned back to his charges after a moment and began another round of chanting: “Can’t drink oil, keep it in the soil.”

One thing seemed clear, as the march progressed. Despite the day’s high temperatures — an omen, perhaps, of the oncoming future — there was a hopefulness to the event: to the signs, the costumes, even the giant puppet show. This was, it seemed, a battle we could win. In fact, that hopefulness is probably what got the march organized in the first place. And what’s wrong with a little optimism, anyway? Even in the sweltering heat, people still showed up in their Arctic best.