"As the hypothermia worsens, people realize even less that they're getting colder," said Bradley. "We see this a lot in people who are alone and don't have anyone to say, 'Hey, you don't look so good.'"
"They are, of course, at high risk and doubly so due to a high percentage of comorbid psychiatric and substance abuse," said McStay.
McStay credited New York City's department of homeless service for its "exceptional" efforts in monitoring of known patients who refuse to seek shelter indoors.
To make matters worse, 20 to 50 percent of hypothermia deaths are associated with paradoxical undressing. Some severe hypothermia sufferers will begin to take off their clothing, which only increases the rate of body heat loss.
"The brain starts playing tricks," said Schneider. "Hypothermic people will think it's hot, and they'll start undressing to cool down."
There is no one way to treat hypothermic patients who come into the emergency room. There are a variety of ways to warm a patient up. Heated blankets that warm the entire body are available in many emergency departments. For patients who are severly hypothermic, doctors may use the same equipment they do for open heart surgery.
Schneider said that she will sometimes circulate a hypothermic person's blood for them through heated coils, or they'll circulate warm saline through the body and give the patient warm oxygen.
Doctors encourage you to dress for the weather, even if you'll only be outside for a minute. Wear layers of light, loose-fitting clothing and carry an extra pair to replace if the first pair gets damp.
Doctors encourage people to stay completely covered when braving the elements.
"Dress appropriately, with numerous layers for warmth," said Sankoff. "Be aware of the wind, as wind chill is a significant issue with lower temperatures."
Those with poor circulation must be extra vigilant, and everyone should avoid alcohol in freezing temperatures, since it increases blood flow to the body's skin, making a person feel warm while the body loses heat.
"Winter can be a glorious time to enjoy the outdoors," said Marshall. "If you wear the right clothes, stay dry, and take a few precautions…you'll keep it that way."