How to Stay Safe in a ‘Heat Dome’

Parts of the United States, including the Mid-Atlantic and the Northeast, are expected to reach record-breaking temperatures as a dangerous “heat dome” settles in for the holiday weekend.

Emergency room doctors are bracing for a double whammy: the typical surge of patients they see on the Fourth of July, many with fireworks-related injuries, and a second influx of people suffering from extreme heat.

To stay safe in a heat wave, “the key is prevention,” said Dr. Bradley Uren, a clinical associate professor of emergency medicine at Michigan Medicine.

Dr. Uren and other E.R. doctors offered tips for how to protect yourself — and others — in the sweltering weather.

Drink more water than you think you need.

“Once you feel thirsty, you’re already behind,” said Dr. Reed Caldwell, chief of service for the Ronald O. Perelman Center for Emergency Services at NYU Langone’s Tisch Hospital. Keep drinking fluids throughout the day, even if you think you’ve had plenty. (One caveat: People with heart failure can end up drinking too much water, potentially leading to fluid in their lungs, so they should follow their doctors’ advice.)

Most people don’t need electrolytes or specialty beverages; plain water is just fine, Dr. Uren said. An important sign that you are not getting enough fluids is dark yellow urine. Certain foods, including fresh fruits and vegetables, can also help boost your hydration levels. Melons, strawberries, oranges, grapes, cucumbers and celery have especially high water content.

As much as possible, avoid alcohol, since it is dehydrating.

Plan your day around the heat.

If you can, avoid being outside from late morning until the late afternoon, which tends to be a hot stretch of the day. Wear light-colored, natural fabrics like cotton and linen and avoid dark colors and synthetic fabrics, Dr. Caldwell said. Spend as much time as possible inside an air-conditioned space. Many cities and towns are making local cooling centers available during the heat wave. (The National Center for Healthy Housing has a directory of these centers.) Public spaces like libraries and malls are also options.

If you do not have air conditioning in your home, use a blanket or sheet on your windows to block out the sun during the day. At night, keep windows open, and run fans to circulate air. You can also spritz your skin with cool or room-temperature water and press a cool cloth to your forehead.

Recognize the warning signs of extreme heat.

“Heat illness is a spectrum,” said Dr. Christopher Bazzoli, an emergency medicine doctor at Cleveland Clinic. Mild, early symptoms can progress into full-blown heat stroke.

One of the earliest signs of exposure to extreme heat is heat edema, or swelling in your ankles, hands and feet, Dr. Bazzoli said. If you notice that type of swelling, head to the coolest place possible — ideally, somewhere air-conditioned. If you have to stay outside, find some shade. Elevating your feet can also help contain the swelling.

Symptoms of heat exhaustion, a moderate form of illness caused by heat, can include nausea, faintness or dizziness, muscle cramps and a racing heart rate. If you are experiencing any of these symptoms, get yourself to a cool place and rest and hydrate. Taking a cold shower or misting yourself with cold water can help lower your body temperature. You can also place cold, wet towels over your body.

A more severe form of heat illness is heat stroke, which can be fatal. People suffering from heat stroke can develop a high body temperature (at or above 103 degrees) and hot and red skin that’s either dry or damp. Symptoms also include headache, dizziness, nausea and a rapid heartbeat.

People with heat stroke often act confused and appear uncoordinated, stumbling and delirious. This is frequently coupled with rapid, shallow breathing. If someone is exhibiting these symptoms, call 911 immediately and try to move the person into a cooler area or shade.

Closely monitor people who are especially vulnerable.

Certain groups are particularly at risk for developing heat-related illnesses, including older people, infants and pregnant women. Those with conditions like heart disease, lung and kidney issues and diabetes are also more susceptible.

Note that some medications can raise the risk of dehydration and heat-related illness. They include certain blood pressure drugs, allergy medications, thyroid hormone replacement drugs and antipsychotics and antidepressants.

Protect your pets, too.

Keep your pets inside as much as you can — ideally in air conditioning or, failing that, at least near a fan. If your pets must stay outside, ensure they have plenty of shade and fresh water and do not leave them unattended for more than a few minutes. Watch out for warning signs that your pet is overheated, including excessive panting, atypical lethargy, vomiting or extreme diarrhea. If your pet exhibits these symptoms, seek medical care for them as soon as possible.