Here's how to keep cool and stay safe during this week's heat wave hitting millions

Scorching heat is about to hit large swaths of the Northeast and Midwest, bringing multiple days of temperatures above 90 degrees Fahrenheit and heat advisories for millions from Ohio to New York to Maine.

Humidity will likely make the heat feel hotter in some places, forecasters warn, and days of near-record temperatures may strain energy infrastructure, increasing the risk of dangerous power outages that could leave people without air conditioning.

If you get too hot and can't cool down and get your body's temperature back to a normal level, you could quickly become at risk for heat exhaustion, or worse, heatstroke.

Experts say preparing and adapting your daily routine for the prolonged heat can help ensure your health isn't put at risk. As it heats up and many rely on fans and air conditioning more than ever, here are some tips to stay cool.

Easy ways to keep cool in hot weather

It is important to limit any kind of outdoor activity during the hottest parts of the day, according to Bianca Feldkircher, lead meteorologist at the National Weather Service in Phoenix. If you can avoid going outdoors during those times, try to put off activities until the morning or after the sun goes down.

Older Americans, people who work outside and those who take medications for things such as heart disease and blood pressure are among those at the highest risk for heatstroke, Dr. Fred Campbell, a professor at the University of Texas Health Science Center in San Antonio told USA TODAY during a similar mid-June heat wave in 2022.

Certain medications, including those to treat schizophrenia, can interfere with the body's ability to regulate temperature. For older Americans, the risk is also high because the ability to regulate your body's temperature declines with age, Campbell said.

There are easy ways to cure being overheated. Getting inside and into the air conditioning is always helpful, along with finding some shade and drinking lots of water. According to the Red Cross, on average, a person should drink approximately 3/4 of a gallon of liquids per day.

When it comes to hydrating, it's best to drink water with added electrolytes, Dr. Ryan Lamb, medical director at UNC Rex Hospital in Raleigh, North Carolina, told USA TODAY in 2022. Capsules or tablets used to flavor water are an easy way to add a little bit of salt, as opposed to buying sugary sports drinks.

Eating foods that have a high water content, such as fruits and vegetables, can also keep you hydrated, Feldkircher said.

Surfaces help too, like sitting in cool grass as opposed to hot black asphalt. Or, even hanging out in a pool or in the ocean. 

What if I don't have any AC?

If you live somewhere without air conditioning, experts recommend opening your windows at night and closing them before the afternoon heats up. 

Typically, the peak hours when most areas see the hottest weather is from 1 p.m. to 6 p.m. That's when it's most important to try to keep cool, even if that means finding refuge in a business or restaurant or carrying around a fan or spray bottle to cool off. 

When it comes to older Americans and young children, who can't regulate their temperature as well, having multiple fans "directly blowing" on them can make a big difference, Campbell said.

How the heat wave can impact your health

During extreme temperatures and heat waves, people may experience dehydration, heat exhaustion and in the most extreme cases,heatstroke.

Your body is always trying to set your internal temperature, so when it's hot outside you cool off through sweating − but that bodily process can be less effective during a heat wave.

When your sweat evaporates, it takes heat away from your body. But when it's humid, sweat has nowhere to go and doesn't help in cooling a person off as much, Lamb said.

"The water can't evaporate into anywhere, because it's already in the air and so there's nowhere for the moisture to go," he said.

When that happens, people can start to experience heat exhaustion. While that can be mild, severe heat exhaustion − known as heatstroke − can turn deadly. Heatstroke happens when your body becomes unable to control its internal temperature. 

But noticing signs of heat exhaustion can be challenging, Lamb said.

"The one unfortunate thing is that we don't necessarily see you progress from mild to moderate to severe," he said. "So unfortunately, sometimes you could spend the afternoon with someone and then you turn around and realize they're 'severe' and you didn't see any other symptoms."

Signs of heat exhaustion include:

• Heat rash, which can be itchy
• Swelling in the hands and feet
• Passing out

Signs of severe heat exhaustion include:

• Feeling sick to your stomach
• Cramping 
• Confusion

If you see any signs of confusion, or someone being disoriented, seek immediate medical attention, Lamb said.

How long can heat exhaustion last?

If your symptoms worsen within an hour, you should seek medical attention, according to experts.

Recovering from heat exhaustion can take between 24 to 48 hours, according to Mount Sinai. If you are still not improving within that time, see a doctor.

How can I keep my dog cool during a heat wave?

Hydration is key when keeping your dog cool in the heat, and it is vital for them to drink the right amount of water every day.

You should also avoid taking your dog out during the midday heat, according to Purina. The middle of the day tends to be the hottest in terms of temperature, particularly around 3 p.m. It's best to keep your pet out of the sun at that time and bring play and exercise indoors. 

Be sure to have good air circulation in your home. Have air conditioners and fans to cool your space on hot days, says the American Kennel Club and Blue Cross.

Wetting your dog is a solution to the heat, according to Blue Cross. Whether your dog is ready to jump into the water or it needs some coaxing, wetting your dog's coat can effectively cool them down. Even if your pup just dips its paws in, the water will be absorbed, and heat will be released through its paws.

Dogs do not sweat like humans, so it is hard to exactly pinpoint when they are overheated.

Some signs to watch out for include frantic panting, extreme salivation and labored breathing, according to the American Kennel Club. When a dog starts to get hot, blood will rush to the surfaces of the tongue, gums and membranes to get rid of the excess heat.

If these symptoms go unnoticed, a dog's mouth will turn grayish to purple from low oxygen levels, and the dog will struggle to breathe.