NEW YORK (CBSNewYork) — If you’ve been outside already, you know it is cold. If you haven’t, bundle up.

Tuesday was coldest day of the season so far — so far! While the cold is just an inconvenience for most of us, for some it poses  a serious health hazard. Here’s what you need to know to stay safe in the cold, Dr. Max Gomez reports.

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The most important thing is the obvious one: stay out of the cold as much as possible.

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If you have to walk anywhere, like to the bus or subway, duck into a warm building from time to time to warm up. But if you do have to be outside more than a couple of minutes, the first thing to remember is to dress in layers. Multiple warm layers trap warm air better than one big heavy layer.

And stay dry, because wet layers sap heat dangerously fast.

Wool is good because it doesn’t lose its insulating properties, even if it does get wet.

Your body needs fuel to stay warm so don’t forget to eat. Drink water too because cold air is very dry. And watch for that telltale sign that the cold is becoming more than uncomfortable.

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“You shiver to generate heat. So if you feel that you’re shivering you need to get out of the cold and get inside and warm up. If you’re shivering and somehow manage to stop shivering then that’s a sign that you’ve gotten even colder,” said  Dr. Jeffrey Rabrich of St. Luke’s-Roosevelt Hospital.

“And that’s not a good sign if you stop shivering, that means get inside right away. Because you’re very cold and you need to warm up.”

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Basically you want to cover all the exposed skin that you can. Gloves of course keep your hands warm. Mittens are even warmer because you don’t have all this surface area to lose body heat from. A scarf is important to keep the heat trapped down under your coat and protect your neck where all that blood flow is.

Which means you’re going to lose a lot of body heat.

If your ears get cold very cold, either pull on a hat, a hood or try some ear muffs. Your head is where you’re going to lose most of your body heat, again because there’s a lot of blood flow there.

Hair is a little bit of an isulator, but if you’re a bit follicularly challenged, a hat is especially important.

And while most of us will get through this just fine, OK, maybe a little grumpy, there are some folks who need to extra careful.

“The elderly and children need to be particularly careful to avoid the cold. As we age, and young children as well, we can’t regulate our body temperatures as well as we do,” said Dr. Rabrich.

Which means they can develop frostnip or frostbite earlier than others.

The first signs of that are numbness and tingling in fingers, toes or exposed skin. If they then start to get grayish or white, get inside right away but don’t rub the affected area as you’ll damage your skin.

Warm water can re-warm the area but not hot water because you can’t feel the heat and you could easily burn the numb area.

Hypothermia symptoms include drowsiness, loss of coordination, confusion and of course uncontrolled shivering, or later, no more shivering. All are serious. Get in a warm place, drink warm fluids and seek immediate medical attention.

Hypothermia can lead to abnormal heart rhythms, coma and even death. Although, again, that’s rare these days.

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And if you’ve suffered some frostnip or frostbite, don’t re-expose those body parts to the cold. They’re more susceptible to cold injury at that point.

Tony Aiello