THOUSANDS OF environmental activists and Bernie Sanders loyalists jammed the sweltering streets of Center City in separate marches Sunday on the eve of the Democratic National Convention.

Both demonstrations were peaceful amid a huge police and fire department presence, with throngs refreshing at cooling stations and sprinklers spraying mists of water from fire hydrants. At one point, protesters thanked and waved to police and fire personnel.

Sanders crowds, already angry over WikiLeaks' posting of 19,000 DNC emails that suggest Democratic officials favored Hillary Clinton over Sanders during the nominating contests, erupted in joy upon hearing that DNC Chairwoman Debbie Wasserman Schultz would step down after the convention. Sanders had called for her resignation hours earlier.

"Goodbye, Debbie" and "Debbie Is Gone" were chants midway through the march from City Hall down Broad Street to FDR Park.

"It's a good first step," said Chris Holl, 33, from San Francisco. ". . . But they're doing it as a concession to save the party."

Barbara Clarke, 72, of Sebastopol, Calif., said she was ecstatic that Wasserman Schultz would be out.

"The whole DNC has to do a redo," Clarke said, adding that the party "has undermined Bernie's campaign from Day 1."

One dejected Sanders loyalist, Paula Iasella, 61, of southern New Hampshire, lugged a 3-by-4-foot double-faced sign on a 7-foot-tall aluminum pole. The front of the sign was a portrait painted of Sanders with the message #stillBernie; the back, a silhouette of Sanders with his fist raised and the words "US DemExit."

Iasella said she is leaving the Democratic Party after 42 years.

The phalanx of environmentalists sweating in the March for a Clean Energy Revolution said they were pushing for the nation's "current and future leaders" to ban fracking now, keep fossil fuels in the ground, stop dirty energy, transition to 100 percent renewable energy, and ensure environmental justice for all."

As temperatures rose to 95 and beyond, Bill Snape of Washington marched from City Hall to Independence Mall while remarkably remaining in costume - a head-to-paw polar bear suit - and on message.

"I'm in much better shape than the polar bears of the Arctic," said Snape, a law professor at American University and volunteer with the nonprofit Center for Biological Diversity, as he cradled the furry bear head above his shoulder for a moment of respite. "Their habitat is literally melting, melting precipitously."

Police estimates ranged from 5,000 people to twice that as the energy march poured down Market Street, snarling traffic in every direction.

Organized by Americans against Fracking, the event was one of the first of several marches that will fill the city's streets during this week's DNC.

The venue for this one was fitting: Pennsylvania is the nation's second-largest producer of natural gas, almost all of it produced by fracking - high-powered water drilling - of the Marcellus and Utica Shale formations. Environmentalists are concerned that the process utilizes a cocktail of chemicals, some of them known carcinogens, forced at great pressure with millions of gallons of water deep into the Earth, followed by the return of contaminated, briny fracking water that is difficult to dispose of safely. Critics also say the process threatens to contaminate underground aquifers.

"Our vision for the future is keeping fossil fuels in the ground," Wenonah Hauter, executive director of Food and Water Watch, yelled to a mass of cameras and microphones at a pre-march news conference, sparking chants from the surrounding crowd of "keep it in the ground."

Nearby in the City Hall courtyard, John Bito helped his wife, Patty Bicknell, spread sunscreen on her back before the march took off. The Seattle couple went fossil-fuel free 10 years ago, powering their Volkswagen Bug with vegetable oil instead of gas.

Today they mainly drive an electric car designed, not rigged, to be environmentally friendly. And they've seen a mind-set long embraced by their city spread across the nation.

"Coming here and seeing all these people from all over the country, it just gives me hope," said Bicknell, who, like her husband, is a Bernie Sanders supporter. "You get in this mind-set like, it's just you. But then you realize, 'Oh my god, there are so many people who think like us.' "

Though fighting fracking was the event's main draw - and speakers implored Gov. Wolf and Democratic Party leadership to ban fracking and invest in renewable energy - hundreds of groups with varying rallying cries took part.

Forest Happel, 60, of New York City, wore a papier-mâché fish on his head, a reference to efforts to clean up the Hudson River.

Bri Dinan, a 23-year-old from Philadelphia who recently started an eco-friendly cleaning-supply company, said her focus was air quality and the nation's overreliance on chemicals.

Taylor Quinn, who at first identified herself only as sunny flower from "planet Earth," said she was there "repping love," because "the Earth needs love."

Among the more colorful Sanders boosters were a pair of self-ordained New Age "nuns" who identified themselves with business cards as Sister Darcy, 53, and Sister Kate, 25, of the Sisters of the Valley in Merced, Calif.

"We are here to protest the corruption of the Democratic Party," Kate said.

Dressed in white and lavender habits, the two were sharply critical of the party and of Clinton.

"The DNC chose Hillary," Darcy said. "The people didn't. People say that voting Green or writing in his [Sanders'] name is a vote for Trump. But it's not on us - it's on the party."

Jessica McDonough, 25, of Philadelphia, said neither major party candidate would get her vote.

"I can't vote for Hillary or Trump," she said.

Once they reached FDR Park, the Sanders supporters searched out shade to rest and regroup as music and more speeches filled the oppressively humid air.

City officials were so concerned about dangerous health conditions from the heat and high humidity - the heat index was expected to exceed 100 degrees Sunday and 105 degrees Monday - that Mayor Kenney urged visitors to limit their time outdoors as much as possible and to take advantage of city-provided cooling centers, spray grounds, or public pools. He also warned of thunderstorms and said safety personnel would direct demonstrators to shelter areas until storms passed.

"For the safety of demonstrators during the DNC, two medic tents, two misting tents, and bottled water will be available in FDR Park," he said. Medics were assigned to the marches.

By nightfall, at least a dozen camping tents had been pitched on FDR Park grounds in apparent defiance of the city's insistence that the park not be inhabited overnight.

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@TriciaNadolny