A summer jaunt to Europe used to be the norm for high school graduates, or affluent families enjoying a few weeks off.

That timeworn tradition is in danger, industry experts warn, as crowds under the Eiffel Tower and the Colosseum become notably less American between May and August.

And there’s one simple reason for the change, in-the-know types say — record-breaking high temperatures across the continent are sweating people out.

“The weather in Europe in August is really hot….people who have choices when they can take their vacations are moving into, let’s call it, more temperate months,” Delta Air Lines President Glen Hauenstein said Thursday on an earnings call, according to NBC News.

The sizzling situation is “continuing to shift travel to Europe in particular from July and August peak to a September and October peak,” he explained.

This summer, the Northern Hemisphere reported the hottest temps on record, according to the European Union’s climate monitoring agency.

The heatwave beat out last year’s record-busting highs.

In response, airlines are now expanding their flight schedules to accommodate travelers’ shifting habits.

Patrick Quayle, United Airlines’ senior vice president of global network planning and alliances, announced that the company would be “extending the season.”

The airline began flying some European routes in March and April this year, some of which will now continue through late October and early November. 

“What we’re seeing is, more and more, travelers are going in those shoulder seasons where you can get a bit more value, and I think the weather’s a bit better,” he added.

As the climate shifts, it’s also changing where in Europe people want to go.

Travelers have begun to show less interest in hotter Mediterranean countries — instead booking trips in locales with more moderate temperatures, like Scandinavia, CNN reported.

Overall, however, tourists continue to descend on Europe in large numbers throughout the year — much to the dismay of many locals.