They put on a gritty war face and insist they are more determined now than ever, but the Occupy Wall Street campers now face the slow advance of an unrelenting enemy: the New York winter.

As freezing winds blew Friday over the epicenter of their protests, Zuccotti Park in Manhattan, the demonstrators were already huddling in significantly reduced numbers.

At night, the several hundred people who sleep on site in the financial district bundle up as best they can under plastic tarps, hunkering down in sleeping bags and emergency blankets as tents are forbidden on the plaza.

Many sleep with bonnets and scarves. But the worst has yet to come.

"So far, we have been extremely blessed," said Cynthia Villarreal, who has slept at Zuccotti for 18 days.

Ever since the anti-corporate protest movement began on September 17, OWS has only battled a handful of rainy days. At night, temperatures are still above freezing.

But New York winters often see frigid temperatures that drop below 14 degrees Fahrenheit (-10 Celsius).

"The cold affects us already," admitted Maria Fehlig, a volunteer nurse at the protesters' makeshift infirmary, a small blue tent marked by a cross that is the only structure so far tolerated by owners of the park ensconced between skyscrapers.

She noted there had been several cases of hypothermia and respiratory problems. An online petition is asking Mayor Michael Bloomberg to allow protesters to erect tents on the plaza, though it has not yet been sent.

It is unlikely to succeed.

"The Constitution doesn't protect tents, it protects speech and assembly," Bloomberg said in a press conference Monday amid growing frustration by some New Yorkers as the protesters continue camping out in the heart of global finance.

Bloomberg has also predicted that the weather would play a role in determining how long the movement will last.

But Fehlig, who has been helping protesters learn basic methods to resist the cold, insisted that they formed "a determined group that plans to stay until it changes."

She tells demonstrators to stay dry, wear hats, layers of clothing and good pairs of socks and gloves.

The protesters' kitchen, which serves at least 2,000 meals a day, according to cook Chris O'Donnell, offers warm food ordered from nearby businesses or cooked by volunteers with the help of donations.

"We use a soup kitchen in East New York," explained O'Donnell, an OWS supporter known as a "point person" as the group does not recognize any official hierarchy.

But he also acknowledged that there is a definite lack of abundance on cold and rainy days.

And OWS has yet to organize a major protest since thousands of people gathered in Times Square on October 15 chanting "We are the 99 percent."

The movement that denounces global greed and the richest one percent continues to broadcast its protests online, often live, but the number of people watching has markedly dropped, along with the number of tweets about the site.

The next stage for this leaderless movement, which sees itself as independent of political parties and claims no particular demands, remains unclear for now.