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Keep cool, even if you don’t have air conditioning

Staying cool and hydrating often are the two most important things you can do to avoid feeling sick and discomfort when it’s extremely hot. If you don’t have an air conditioning unit, or if your A.C. has been on nonstop and you still feel hot, here are ways to cool your body and home:

• Spritz your skin with a mist of cool or room-temperature water.

• Block out the windows in your home — especially those that get afternoon sun — with a blanket or a darker sheet during the day to keep the heat out.

• If you don’t have A.C., keep windows open at night and run fans to circulate the air. Wirecutter, a New York Times company, has guidance on the best products to keep your home cool.

• Wipe your forehead with a cool cloth.

• Avoid strenuous exercise outdoors if possible.

• Put ice cubes in your water bottle, especially if you’re outdoors.

• Avoid using your stove or oven if possible.

Watch for signs of heat exhaustion

Watch out for symptoms of heat exhaustion, which in adults include heavy sweating; cold, pale and clammy skin; a fast, weak pulse; nausea or vomiting; muscle cramps; fatigue; dizziness; or headaches and fainting. (More on symptoms in children below.) If you are experiencing these symptoms, sip water, move to a cooler location if possible, loosen your clothes, or try to take a cool bath or place cool, wet cloths on your body. Seek medical attention immediately if you vomit or if your symptoms worsen or last longer than an hour.

Recognize the signs of heat stroke

The symptoms of heat stroke include a high body temperature (103°F or higher); hot, red, dry or damp skin; a fast and strong pulse; a headache; dizziness; nausea; and fainting.

A person with heat-related illness may start stumbling or appear less coordinated than usual. Ask the person if they have a headache, nausea or dizziness. Talk to them about a variety of topics to see if they exhibit symptoms of confusion.

If someone is experiencing these symptoms, call 911 immediately, and try to move the person into the shade or a cooler area if available; use cool cloths or a cool bath to lower their body temperature.

If you suspect a person is having a problem with the heat, err on the side of caution and get them somewhere cool. Have them drink water and spray their body with cold water or rub them with ice or a cold cloth. If they don’t cool down quickly, seek medical advice.

Stay hydrated

There’s not a one-size-fits-all rule for the amount of water to drink, said Dr. Adriana Quinones-Camacho, a cardiologist at N.Y.U. Langone Health. But everyone should expect to drink more than they normally would when it’s very hot outside. Drink even when you’re not thirsty. Since we lose electrolytes when we sweat, drinking Gatorade or other sports drinks with electrolytes can also help, she said.

To ascertain how much water you should drink, “you want to watch your output,” said Dr. James Mark, an emergency medicine physician in Cleveland, Ohio. If you’re urinating less frequently than normal, that’s a sign you should drink more fluids.

Avoid consuming alcoholic or caffeinated drinks, which can be dehydrating.

Eat foods to help you cool off

Fruits that have water in them, like watermelon, can help you fend off the heat, Dr. Quinones-Camacho said. If you’re having salty food, drink extra water to balance it out. Try to stay away from hot foods.

Keep kids safe in the heat

Young children are especially vulnerable to heat-related illnesses. Parents and caregivers should monitor their activity during hot weather and plan activities that are less likely to cause them to overheat, like running through sprinklers or playing in a pool. Also make sure kids are wearing lightweight, light-colored clothing, using sunscreen and hydrating regularly.

If a child is playing outside of the water, try to keep them in the shade and consider bringing a spray bottle to spritz their skin (and your own).

When it is humid and 90 degrees or hotter, children should not play outside for more than 30 minutes at a time. Keep babies under 12 months out of the sun as much as possible.

Teens tend to be more active than adults in the summer, Dr. Mark said, and should plan activities like hanging out in a park before noon, when the heat will be less intense.

What are the signs of heat exhaustion in children?

If a child develops heat exhaustion, she may start to feel dizzy and nauseated, suffer muscle cramps or begin vomiting. Her skin may feel cold and clammy to touch.

If you observe these symptoms in a child, bring her to a cooler place; ask her to sit still or lie down; remove excess clothing; apply a cool, wet cloth or water to her skin and give her water to drink.

What are the signs of heat stroke in children?

“In heat stroke, the skin is hot and dry instead of cold and clammy, and the child gets sleepy and maybe confused,” said Dr. Claire McCarthy, a pediatrician at Boston Children’s Hospital and an assistant professor of pediatrics at Harvard Medical School. Children with heat stroke may also experience a high fever or seizures. They don’t necessarily sweat.

Children who haven’t exerted themselves at all can still be at risk of heat stroke if they are dressed too warmly in a hot environment, are in a hot vehicle or in a room that doesn’t have any circulation or are out in the sun at the beach, said Dr. Tony Woodward, the medical director of emergency medicine at Seattle Children’s. “All of those kinds of things can lead to their temperature going up very quickly.”

If you suspect that a child has heat stroke, call 911 and try to cool them down until help arrives.

Keep pets cool

Here are some simple precautions to protect dogs and other animals:

• Walk your dog early in the morning or after sunset when the air and the streets are cooler. Avoid strenuously exercising your dog on very hot and humid days, and seek out shady trails or sidewalks whenever possible.

• Always carry water and a bowl. Stop often to make sure your pet is sufficiently hydrated; panting, which is how they lower body temperature, causes water loss.

• If your dog slows down or stops, let them rest and take frequent breaks.

• If your dog shows any signs of overheating — excessive panting, lethargy, a deep red tongue — get them into cool water as soon as possible. A cool wet towel or piece of clothing can also help.

• If signs of distress persist, go to a veterinarian immediately; organ failure can be rapid and fatal.

• Keep your pets groomed.

• A cooling mat can also give your pet respite.

Protect older people from heat

Dr. Wayne McCormick, a gerontologist at the UW Medicine in Washington, said the key advice for older people is to stay hydrated. If their home isn’t cool, try to get them to a public cooling center or an air-conditioned space like a mall.

If an older person shows signs that they are weak, tired, dizzy or nauseated, seek medical attention, Dr. Quinones-Camacho said.

Sleep soundly in the heat

Use a breathable cotton sheet, Dr. Mark said. You can set up a fan near your bed and spray your sheet with cold water before sleeping, or place your pillow cases or sheet in a plastic bag and store in a freezer during the day. A cold bath or shower right before bed can also help.

Hydrate before heading to bed, and if you wake in the middle of the night, drink water, Dr. Quinones-Camacho said.

Additional reporting by Tara Parker-Pope, Christina Caron, Gretchen Reynolds and Caitlin Kelly.