It was the middle of July, peak summer travel season, and the news from Europe wasn’t looking good: A heat-induced “surface defect” briefly closed the runway at London’s Luton Airport. Trains were delayed or canceled across Britain because of overheated tracks. More than two dozen weather stations in France recorded their highest-ever temperatures. And wildfires blazed in tourist regions of France, Spain, Portugal, Italy and Greece, including just outside of Athens.

“If you were in the center of town, you could look out and see the Acropolis, and in the distance you could see the red haze,” said Peter Vlitas, an executive vice president at Internova Travel Group, who was in Athens during the wildfires, which firefighters have since brought under control.

Mr. Vlitas added that he could smell the smoke from his hotel and sometimes had to close his door to prevent fine ash from blowing into his room. But life in Athens, he said, went on pretty much as usual.

“The taverns are full at night and the cabbies are busy, which is always a great barometer,” said Mr. Vlitas, still in Athens. “Greece is experiencing what the rest of Europe has — a record number of tourists.”

After more than two years of putting off their vacations, travelers are loath to cancel their trips, even in the face of headline-making weather. But several people in the industry described a growing number of travelers who are adjusting their plans to account for high temperatures, whether by swapping out destinations, reworking their daytime schedules, or delaying their trips by a month or two.

Given the pace and trajectory of climate change, such shifts are likely to become more common — and more necessary — in the years ahead. That’s especially true for travel to Europe, a region that climate researchers have described as a “hot spot” for severe summer heat, and where they predict that future heat waves will be longer, more frequent and more intense.

Even with this summer’s high tourist numbers, there are already subtle signs that the heat is driving changes that could become the future norm. Europe’s summer travel calendar has begun to stretch into the quieter (and cooler) months of April, May, September and October, while many travelers are starting to shift their itineraries northward and toward the coasts.

Karen Magee, a senior vice president and general manager at In the Know Experiences, said that, beginning in mid-July, her travel agency started getting calls from clients asking if they could adjust their travel plans to account for the heat.

“That was new,” Ms. Magee said. “I can’t remember the last time we had people calling and saying, ‘Maybe we’re going to skip Rome and opt for a more beach-accessible city.’ Or maybe they shortened their itinerary in the city and opted to go into the country a little sooner than they had planned.”

Dolev Azaria, the founder of Azaria Travel, helped one family make the last-minute choice to spend the first five days of their vacation in Amsterdam instead of Rome, just to avoid the heat. Other clients scrapped their plans for Tuscany and rebooked for Sicily, where at least they would have a Mediterranean breeze.

“The goal is to move a client from any heat-trapped city to a waterfront vicinity,” Ms. Azaria said. “So places like Copenhagen and Amsterdam have come up, places that maybe our clients wouldn’t have originally chosen to go to.”

But Ms. Azaria said that, so far, she hasn’t had any complete cancellations: “There’s been so much pent-up demand. We’re basically condensing two years of travel into this summer.”

Looking ahead to next year, Ms. Azaria is planning for an elongated summer travel season: “We’re already seeing that summer really extends through the end of September, even until mid-October,” she said.

Any travelers who might consider bailing on a trip because of extreme heat may discover that their cancellation policies leave little opportunity for a refund. Clients of Jude Vargas, a travel adviser and founder of Pyxis Guides, were worried about the heat on an upcoming family trip to Portugal, but they ended up sticking with it.

“They were concerned about their kids being outside,” Ms. Vargas said. “But because of the cancellation policies, they just realized, ‘OK, we’re committed.’”

Even travel insurance is unlikely to cover travelers who cancel a trip because of a heat wave, said Dan Drennen, director of sales and marketing at Travel Insurance Center. The only policy that would apply in such a scenario is “cancel for any reason” insurance, Mr. Drennen said. He added that this kind of insurance is typically about 40 percent more expensive than normal coverage, and it generally refunds a maximum of 75 percent of the total trip cost. He advised travelers to do their research and speak to a broker before they buy insurance, so they understand what’s covered and what isn’t.

“People assume that these policies do everything, and they don’t,” Mr. Drennen said.