Temps of up to 95 degrees are expected this weekend as an icky, sticky “heat dome” is expected to engulf NYC. The New York City Emergency Management Department and Department of Health and Mental Hygiene has announced the opening of cooling centers Friday and Saturday which can be found by calling 311 or checking nyc.gov/beattheheat — an omnibus of hot weather coping strategies.

amNewYork spoke with Dr. Susi Vassallo, a national expert on heat-related deaths and a clinical professor of emergency medicine at NYU Langone Medical Center, about avoiding heat exhaustion and heat stroke, the most extreme and dangerous form of heat illness.

When do we need to worry about heat-related illness?

When the heat index — a combination of temperature and relative humidity — reaches 88 degrees Fahrenheit. That could actually be less than 88 degrees. If humidity is very high, the human body cannot cool itself off as effectively.

Who is most likely to wind up in the ER as a result of heat illness?

In New York, elderly people who don’t have or don’t use air conditioning. Many older people underestimate their risks and they may have illnesses that don’t allow their bodies to cope as well with heat extremes. But all people with underlying conditions such as asthma, emphysema, diabetes, COPD and other cardiovascular diseases are more likely to wind up in the ER during heat waves because their conditions often worsen in the heat — asthmatics may wind up having to use their inhaler more often, for example. Diabetes is an enormous risk: It’s a disease of the small blood vessels which ideally should expand and dilate to cool the body, but in diabetes the function of these blood vessels is impaired. Also, the medications taken by diabetics and many patients with cardiovascular and other diseases impair the ability of the body to cool itself. People who are mentally ill or homeless are at two to three times the risk of winding up in the ER from heat stroke.

What about younger, healthy people?

Heat stroke is the number one cause of death in high school football players in America. We have had many deaths of young, healthy people in the military who were pushing themselves or being pushed to exceed their limits. When it’s hot out, your body is already trying to get rid of the heat — heat in has to equal heat out! — but if you are exerting yourself physically, you’re creating so much energy the heat can’t dissipate.

What are the warning signs of heat exhaustion and heat stroke?

It’s usually weakness, sweating, a feeling of thirst and feeling faint or dizzy. Heat cramps are also present on the heat illness spectrum and headaches and a sense of disorientation can also develop. As one gets sicker, one can even develop chills. Heat stroke is when you have a body temperature of 105 degrees — your body can no longer take care of itself — and your mind no longer works. It’s very serious and it doesn’t take long to develop. Within half an hour you can go from having no symptoms — talking, joking around — to having heat stroke.What do we do if we have any of these symptoms?

If you’re exerting yourself, stop the physical activity immediately: You’re generating heat! Get to a cool, shady place and if you have any water, wet yourself — wet your head, face, shirt and clothes to increase your evaporative cooling.

What about hydration?

It’s important to stay hydrated in the heat, but just drink to thirst. People read they have to stay hydrated but then drink so much water they get hyponatremia, a condition in which their sodium levels become too low. Sports drinks are a waste of money: Water is best.

Anything else?

A heat wave is a public health emergency. We are all responsible for helping to prevent deaths just as we are to alert others to fires if we smell smoke. Check on your elderly neighbors and make sure they have access to air conditioning. If you see homeless people laying around in the heat, bring them a cold drink and remind them to get to a cool place!