DO: Know the symptoms of heat stroke. According to the CDC, signs of heat stroke, also known as hyperthermia, include:

• Body temperature of 104 degrees Fahrenheit or more (40 degrees Celsius)
• Fainting
• Confusion
• Fast and strong pulse
• Dizziness
• Skin that is hot to the touch. The skin may also be red, dry, or damp.
• Upset stomach, nausea, or vomiting

DO: Call 911 immediately if someone is showing heat stroke symptoms. Heat stroke is a medical emergency. In the U.S., dial 911.

While you wait for help, the CDC recommends that you provide first-aid treatment:

• Move the person to a cooler place out of the sun.
• Cool the person by applying cold, wet cloths or by placing the person in a cool-water bath.

DON'T: Do not delay care, even if you are worried that the person may contract COVID-19, the disease caused by the novel coronavirus. Hospitals are working to protect patients during the pandemic, for example by limiting visitors and separating COVID-19 patients from others.

DON'T: If a person is showing heat stroke symptoms, do not force them to drink water or other fluids.

DO: Know the symptoms of heat exhaustion. Heat exhaustion is a less serious condition than heat stroke. But without treatment, it can progress to heat stroke, according to Johns Hopkins Medicine. The CDC lists the following symptoms of heat exhaustion:

• Heavy sweating
• Cold, pale, and clammy skin
• Fast, weak pulse
• Nausea or vomiting
• Muscle cramps
• Tiredness or weakness
• Dizziness
• Headache
• Fainting

DO: The CDC advises you to treat heat exhaustion by taking these steps:

• Move to a cooler place out of the sun.
• Remove or loosen your clothes.
• Cool yourself by applying cold, wet cloths or by bathing in cool water.
• Take sips of water.

• You vomit
• Your symptoms worsen
• Your symptoms do not go away within one hour

DO: To reduce the risk of heat exhaustion and heat stroke, watch the forecast. Heat exhaustion and heat stroke are more likely to occur when the weather is hot, so monitoring the weather forecast is an important prevention step.

Keep in mind that asphalt and concrete absorb heat, so if you live in an urban area with many parking lots, buildings, and other structures, your block may be significantly warmer than other areas of your city.

High humidity is also dangerous. On hot days, you cool down as sweat evaporates from your skin. But when the air is very humid, sweat evaporates from your body only slowly, which prevents it from cooling itself effectively.

When you check the weather forecast, look for the heat index, a number that includes the effects of both temperature and humidity levels. If the heat index is 91 degrees Fahrenheit or higher, you should take steps to stay cool, according to the Mayo Clinic.

• Make sure to drink plenty of water. Avoid caffeine.
• Wear light-colored, loose-fitting clothing.
• Avoid exercising outdoors during the hottest times of the day.
• If you are playing, exercising, or working outdoors, take breaks to cool down under shade.
• If you supervise people who are playing or working in hot weather, offer them plenty of chances to take breaks and drink water.

DO: Seek shelter during heat waves. To stay healthy, your body needs a break from high heat and humidity. If you do not have air conditioning, seek shelter in air-conditioned buildings. Many communities offer cooling centers in libraries and other public spaces. But those buildings may be closed or have limited capacity because of the COVID-19 pandemic, so also consider these options:

• Do you have friends or family members living in an air-conditioned building who would allow you to shelter with them?
• Do you know someone who would allow you to borrow a window AC unit?
• Is your local government offering window AC units or temporary shelter in spaces where self-isolation is possible, such as in hotel rooms?

DO: Know who is most at risk for heat-related illnesses. Anyone may fall ill as a result of overheating, but some people are at special risk:

• Athletes
• Outdoor workers
• People who lack access to air conditioning
• Children
• People age 65 or older
• People who take certain drugs. According to the Mayo Clinic, some drugs may reduce your body's ability to maintain its temperature or hydration levels. Such drugs include beta blockers, diuretics, antihistamines, tranquilizers, antipsychotics, and others.

DO: Understand that global warming is making heat waves more frequent. Carbon pollution from vehicles, factories, and power plants is trapping extra heat in the Earth's atmosphere, much like an overly thick blanket can trap too much heat around you at night. That extra heat is making heat waves more frequent.

In the future, scientists expect that days with high temperatures hotter than 90 degrees Fahrenheit will occur more often. That means that people and communities will need to take more care to prevent heat-related illnesses.

DON'T: Even if you live in the northern U.S., don't assume you are immune from heat exhaustion and heat stroke.

As heat waves become more common, they are occurring even in places that usually experience cool summers, such as northern parts of the U.S. In fact, heat waves in those regions can be particularly dangerous because many buildings lack air conditioning.