(CNN) – Over 50 million people in the southern United States will be under oppressive heat conditions this week. The temperature is expected to climb over 100 degrees Fahrenheit, or 37.8 degrees Celsius, for several days. The heat index, which takes into account air temperature and humidity and is colloquially known as the “feels like” temperature, could soar to over 125 degrees Fahrenheit, which is 51.6 degrees Celsius.As the temperatures rise, there are health concerns associated with extreme heat, including heat exhaustion and heatstroke. Who is most vulnerable and what steps can people take if a heat wave is expected in their area? Are there specific precautions that the elderly and families with young children should take? And how can everyone prepare for hot weather events outdoors?To guide us through these questions is CNN Medical Analyst Dr. Leana Wen, an emergency physician and professor of health policy and management at the George Washington University Milken Institute School of Public Health. She previously served as health commissioner of Baltimore, where her duties included overseeing the city’s “Code Red” responses to extreme hot weather. CNN: What are health concerns associated with extreme heat?Dr. Leana Wen: High temperatures that come with extreme heat can have many serious and harmful health effects. When someone’s body temperature rises as a result of exposure to extreme heat, they could experience heatstroke, which is a medical emergency. Individuals with heatstroke have body temperatures above 103 degrees Fahrenheit. Their bodies stop being able to cool effectively, and they may become confused and dizzy. They have changes in their heart rate and they may faint. These individuals need immediate cooling and emergency medical care; indeed, heatstroke can be fatal. Less severe heat-related illnesses include heat exhaustion, which can progress to heatstroke and heat cramps, which are often associated with exercising in hot weather.In addition to the direct health effects, high temperatures can also put strain on the heart and lungs. The interaction of heat and cardiovascular disease was either the direct or contributory cause in 1 in 4 heat-related deaths since 1999, according to data from the U.S. Environmental Protection Agency. Higher temperatures are also associated with particle and ozone pollution, which have negative health effects, too. CNN: What are symptoms of heat exhaustion and heatstroke?Wen: Symptoms of heat exhaustion include headache, nausea, dizziness, weakness, elevated body temperature and decreased urination. Heat exhaustion is often seen in people working or performing fitness activities for prolonged periods of time in hot environments. If someone is suspected to have heat exhaustion, they should be cooled by getting out of the sun and ideally into a cool, air-conditioned space. Cold compresses and cold drinks will help, too. If the person appears to be confused, fainting or getting worse, call 911 [in the U.S.].Heatstroke is the medical emergency I referenced above. Immediate medical care is essential, and bystanders should not hesitate to call 911 when they suspect heatstroke. CNN: Who’s most vulnerable to heat-related illnesses and what steps can they take if a heat wave is forecast in their area?Wen: Individuals most vulnerable are the elderly and the very young; those with significant underlying medical conditions; and people with social situations that make them more prone to experiencing the harms of extreme weather.Elderly individuals have decreased capacity to adapt to changes in body temperature and are also at higher risk of dehydration. The same goes for young children, who have less physiological reserve and may not be able to reliably report how they are feeling. Individuals with chronic medical conditions are also more susceptible to the added strain placed on them by heat-related illnesses.These more vulnerable individuals should use extra caution during hot weather events. Limit time outdoors when it’s very hot outside. Certainly, do so if your local official has issued a heat advisory, but even if they have not, know your own limits when the weather starts heating up.Try to move fitness activities inside, or if they must be outside, do them in the early mornings or evenings. If you have to be out during the heat of the day, try to stay in the shade. Make sure to use sun protection and drink plenty of fluids. If you start developing any symptoms, like headaches, dizziness, muscle cramps, lack of energy or tiredness, get out of the sun and go inside to cool, air-conditioned places immediately.The other group that’s highly vulnerable are individuals who have specific social circumstances. People experiencing homelessness, for example, or those living without air conditioning, are at high risk because they may not have the option to seek cooler shelter. They should seek out resources from their local and state government, which may provide cooling centers and temporary shelters during periods of extreme hot weather. People who must work outdoors should also use caution as much as possible, including staying well hydrated and aiming to do activities that require heaviest exertion during times of the day when it’s not as hot. CNN: Are there specific precautions that families with young children should take?Wen: First, recognize that young kids often lack the ability to report their symptoms. Children may also become overly excited and want to play outside, even if they are overheating. And they may forget to drink fluids. Especially if you live in environments where your children are not used to hot weather, monitor them closely. Make sure they are drinking plenty of water and consider setting a time limit of 15 to 20 minutes outside in the heat, at which point they must come in and cool down.Second, make sure never to leave kids or pets in the car. The inside of cars heats up rapidly, and sadly, over 38 children die in overheated cars every year in the U.S. Even if you are running a short errand, take children with you and don’t leave them unattended in a closed car. CNN: How can everyone prepare for hot weather events?Wen: In addition to taking steps to prevent heat-related illnesses, everyone should prepare in advance and have contingency plans. For example, if your home’s air conditioning stops working, could you go to a relative’s house or a neighbor’s? Also, what are other weather emergencies that could happen in your area and what will you do if, say, a tornado warning is in effect? Finally, everyone should have a “go bag” of emergency supplies that’s ready for use. Be sure to communicate these plans with your family so that everyone knows what to do. The-CNN-Wire™ & © 2023 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.