"Climate change is going to have an impact, but it's not going to be a doomsday impact," said Michigan State University professor Michelle Rutty, who has researched the implications of warmer temperatures on tourism in Europe and the Caribbean.
She predicted "shifts rather than outright declines" as tourists try to avoid scorching weather.
"If you think of a place like Greece, there may be a shift in time when people travel to these destinations," Rutty added. "They won't want to go in August but now perhaps they'll go in the fall instead."
Rutty said rising temperatures will also affect the demographic profile of tourists visiting certain countries.
Retirees and families with young children may opt to avoid extreme heat due to health concerns, while backpackers aged in their 20s may continue to embrace a very hot beach holiday.
"If prices get cheap, that might be the thing that motivates someone," Rutty said.
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In Spain, the tourism industry has felt the impact of this summer's scorching temperatures.
The Canary Islands, a magnet for sun worshippers, have seen a decline of 1.2 million tourists so far this year, according to Eduardo Parra, president of the Spanish Association of Scientific Experts in Tourism. The islands typically receive around 15 million visitors annually.
"It is becoming apparent that the heat wave in northern and central Europe, together with a redistribution of tourist flows to emerging destinations, is affecting us," he said.
Parra believes tourists are asking themselves why they need to fly to the Canary Islands, which lie some 60 miles off the African coast, if they can find similar temperatures closer to home.
Miguel Pinhâo, who owns a gift shop in the city's Alfama neighborhood, told NBC News there was a clear drop in the number of customers during the hottest hours of the day.
"I think it keeps tourists away from walking," he said.
While the historic area's narrow streets provide plenty of shade, its distance from the city center and location up a steep hill are understandable deterrents for tourists.
Pinhâo said he is adapting to hotter summers, being among the few stores in the area with air conditioning.
"I think it's a good investment because I want customers to be comfortable," he said, adding that residents in the coastal city are also thinking about the long-term implications of hotter summers and rising sea levels.
While Portugal or Spain may increasingly be seen as too hot for some tourists, rising temperatures may increase the appeal of cities that have previously not been considered a traditional summer must-see destination.