NEW YORK (CBSNewYork) — As forecasters have been warning, bitter cold temperatures are dipping into dangerous territory.

So, how long can you stay outside before you risk frostbite?

CBS2’s Dr. Max Gomez reported, true frostbite is pretty rare in cities and suburbs because there’s almost always a warm or sheltered place to duck into.

The exceptions, of course, include homeless people or the occasional case of an inebriated person who passes out in the cold, Dr. Gomez reported.

What a person is more likely to be impacted by is frost nip, an early stage of cold skin damage that could lead to frostbite if you don’t get inside.

To get real frostbite, at the negative-20-degree wind chill that’s forecast, it would take about 30 minutes of continuous exposure to develop frostbite, Dr. Gomez reported.

If you’re skiing upstate where the windchill could reach -40 degrees, the window for frostbite to set in is only about 10 minutes.

But that is for exposed skin, which is why it’s important to keep covered with hats, gloves, ear muffs, scarves and masks for your face.

Signs and symptoms of frostbite include a prickly feeling or needles and pins followed by numbness; the skin turns red and then pale white or grayish and could become hard or waxy looking.

Any of those symptoms should be a red flag to get inside. But Dr. Gomez warns do no rub the affected area. Instead, use warm — not hot — water or air to warm the body part.

It’s toes, ears, nose, and fingertips that are most vulnerable.