Extreme heat is ruining vacations. Here’s how to cope.

This weekend, Italy issued a red alert for 16 cities suffering from dangerously high temperatures, including Rome and Florence. In Greece, authorities temporarily closed the Acropolis in Athens because of a heat wave washing over southern Europe.

Other countries on the continent and across the Atlantic are also withering under the punishingly hot sun. Large swaths of the United States, especially in the Southwest and West, are recording triple-digit temperatures. Heat advisories have become as common as thunderstorm warnings, a harbinger of summers to come.

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“This very well may be the coolest summer for the rest of our lives,” said Ashley Ward, director of the Heat Policy Innovation Hub at the Nicholas Institute for Energy, Environment and Sustainability at Duke University. “With climate change, we are going to see not only heat seasons that start earlier and go longer, but we’re going to see longer and more intense periods of extreme heat.”

More than 60,000 people died last summer during heat waves across Europe, according to a study published by the peer-reviewed journal Nature Medicine, which cited rising temperatures as a “major concern.”

For future trips, travelers might be wise to avoid the hottest months and shift their vacation calendar to spring or fall. Of course, that is little comfort to travelers with flights departing in the next few days or weeks. Here’s some advice on how to stay safe when traveling in sweltering heat.

Before setting out for a road trip, make sure your car is up for the challenge. You don’t want to break down in blistering heat.

David Bennett, AAA’s repair systems manager, said to check the HVAC system, your fluid levels and the tread and air in your tires, including your spare.

Bennett said major rental car agencies in the United States typically stock newer models with air conditioning, but rental car fleets in Europe may not be as current. To improve your odds, book with an international rental company.

As soon as you peel out of the parking lot, allow fresh air to enter the car by turning off the recirculation feature. Once the interior feels cool, Bennett says to reactivate the recirculation button. “Now you’re cooling air that’s already in the cabin and not bringing in that hot fresh air,” he said.

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Once on the road, don’t let the gas needle drop below a quarter tank. You don’t want to get snarled in traffic and run out of fuel on a sunbaked highway. If you are driving an electric vehicle, the air conditioning will drain the battery, so plot a route with frequent stops at charging stations.

For car supplies, pack a cooler with cold beverages and snacks. Bennett also recommends preparing an emergency kit with a cellphone charger; first-aid kit; blanket, in case you need to kneel down on the hot asphalt to change a tire; flashlight with extra batteries; premoistened hand wipes or paper towels; a basic set of tools; and duct tape.

If you dream of cruising along the Amalfi Coast in a convertible, you don’t have to quash that fantasy. Just wear a sun hat and sunscreen, and stay hydrated. If you start to broil, raise the top. You can lower it again for sunset over the Mediterranean.

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Nearly 90 percent of households in the United States used air conditioning in 2020, according to a recent survey by the U.S. Energy Information Administration. But hotel air conditioning is not universal, especially in parts of the Pacific Northwest and Europe.

Shannon Yates, a senior Italy, Greece, Turkey and North Asia specialist with Audley Travel, said about 60 to 70 percent of Europe is air-conditioned. Big-box hotels, international chains and luxury properties are more likely to offer central air conditioning.

“You’ll have a thermostat that you can control,” she said. “It may not go down as cold as you want it to, but you can probably drop it down to about 18 degrees Celsius,” or about 64 degrees Fahrenheit.

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When leaving for the day, she reminds guests that removing the key from the wall switch, which is a common arrangement in hotels abroad, will cut the electricity. To avoid returning to a sauna, close the blinds and draw the curtains.

Staying cool isn’t just an issue of comfort; it’s a health concern. Ward reminds travelers that our bodies need to cool down overnight.

“Pay attention to the daytime temperatures, pay attention to the humidity or the heat index, but really also pay attention to overnight temperatures,” she said, “because the combination of that high exposure during the day and no respite at night is when we see some of the most severe health outcomes.”

Sadly, summer vacation is not the time to sleep in. When planning your day’s itinerary, schedule outdoor activities for early and late in the day, and spend the hottest hours inside.

“At the Acropolis, we get people there at about 8:30 in the morning to manage the heat,” Yates said, “but also to avoid cruise crowds.”

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For national parks, the National Park Service’s trip-planning guide and app (which works offline) offer advice on visiting during the hottest times of the year. The parks also issue alerts, including dire warnings about dangerous heat. For instance, Death Valley National Park, which is experiencing temperatures in the 110-to-120-degree range, warns visitors to not hike after 10 a.m. “Travel prepared to survive,” an alert states.

For hiking advice, rangers can recommend treks with shade or near natural water features, and they can point you toward the nearest drinking water source. Make sure to grab a visitors map, which will highlight all of the park’s amenities, including indoor attractions where you can escape the heat.

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“There is more than one way to experience the park,” said Ina Hysi, an injury prevention specialist with the NPS Public Risk Management Program. “Choose activities that are right for your skill level, and listen to your body. Don’t push it.”

Parks won’t close in extreme heat, but rangers may cancel or suspend programs and outings. Check their calendars online or at the visitors center for current listings.

To avoid standing in line under a bruising sun in cities, book attractions in advance. For general-entry tickets, you may still may need to queue up, so set out early.

“If you get there at 10:30 or 11, the line will be down the hill and around the block,” Yates said of the Acropolis.

Ward reminds visitors to not rush right into activities but to give themselves time to acclimate, just as they would in a high-altitude destination. Also factor in the toils of travel: Flying can deplete your body of energy, sleep and hydration.

“It takes at least two weeks of being in an environment to begin to be acclimated to that environment,” she said.

Though it might seem counterintuitive in the heat, the experts suggest covering up.

Dress in roomy, light-colored garments with good ventilation and built-in sun protection. Yates recommends clothing made by Arctic Cool and Mission, which profess cooling properties. Wear a wide-brimmed sun hat or carry an umbrella. Choose shoes that can breathe, such as sturdy sandals. A small fan that mists is the “it” summer accessory.

“Loosefitting clothing that’s designed specifically for hot environments is probably the best choice,” said Christopher Lemon, assistant professor of emergency medicine at Johns Hopkins University School of Medicine. “This is better as opposed to going bare-skinned with sunblock on.”

Jared Fisher, founder of Escape Adventures, an outdoor adventure travel company, swears by hooded, lightweight dry-tech jerseys with long sleeves and a zippable front. “It’s, like, heaven-sent for me,” he said. “You keep the beating sun off your neck, ears and face.”

The National Park Service’s Hysi holds up park rangers as models of extreme heat fashion, down to their sunbrella hats and misting bottles with ice.

We all know to stay hydrated by drinking lots of water (but not too much) and avoiding diuretics such as coffee and alcohol. Store your drinks in an insulated tumbler to keep them cold. Fisher pops a sodium chloride tablet into his bottled water when he needs an extra boost.

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To lower your body temperature, Ward recommends standing in a cool shower for 10 minutes. In a pinch, immerse your feet and ankles or your arms above your elbows in cold water, a technique used by the military.

“Don’t wait until you are overheated to do them,” she said.

While out and about, frequently wipe your neck, arms and legs with a wet cloth. This will help cool your skin and blood, which is critical to regulating your body temperature. Adventure gear outlets such as REI sell cooling cloths and ties.

Parents with children need to take extra precautions. They should forgo baby carriers and wraps, which can turn into an oven. Ward said that, in addition to exposing children to the hot air, you are also covering them in an extra layer of clothing, plus radiating your own heat onto them. Instead, she recommends using a stroller with a canopy and clip-on fan. Do not cover the opening with a blanket or sheet.

“You should always try as much as possible to keep the wind blowing on your baby,” she said.

Jennifer Hassan and Ellen Francis contributed to this report.

Our warming climate: In July, Phoenix set a national heat wave record for the hottest month ever in a U.S. city. Heat waves are ramping up the global burning of fossil fuels, as July will be Earth’s hottest month on record. Here’s why the sweltering heat wave isn’t moving anytime soon. Use our tracker to see your city’s extreme heat risk. Take a look at what extreme heat does to the human body.

How to stay safe: It’s better to prepare for extreme heat before you’re in it. Here’s our guide to bracing for a heat wave, tips for staying cool even if you don’t have air conditioning, and what to know about animal safety during extreme heat. Traveling during a heat wave isn’t ideal, but here’s what to do if you are.

Understanding the science: Sprawling zones of high pressure called heat domes fuel heat waves. Here’s how they work. You can also read more about the link between weather disasters and climate change, and how leaders in the U.S. and Europe are responding to heat.