The prolonged heatwave in Europe has made TUI “cautious” about its forecast for the fourth quarter to September and full-year financial results.

But TUI chief executive Fritz Joussen dismissed concerns about the impact of a no-deal Brexit despite confirming the group has made plans to handle the fall-out if the UK exits the EU next March without a deal.

TUI reported “a very good nine months” in third-quarter results released on Thursday, maintaining its forecast of 10% growth in underlying profit over the financial year despite a fall in profits in the UK in the three months to June.

However, Joussen said: “We are cautious people. How much the hot weather will impact the last quarter remains to be seen. Hot weather is usually not the best environment for last-minute bookings.

“Outperforming 10% is a little unlikely. But we are 86% booked [for this summer]. We have so many bookings in, we can be confident at least of 10%.”

He added: “Historically, we know if the weather is very hot, late bookings are low and we have seen the last five weeks very good weather.

“But we are 4% up [for bookings] with 86% of bookings in, so we re-iterate our guidance.”

Asked whether the heat might deter people from booking to the Western Mediterranean, Joussen said: “There is no evidence for that. People also go to Egypt and it can be 40 degrees there. But good if people go [instead] to Turkey.”

He dismissed concerns about a no-deal Brexit and denied TUI had ramped up preparations for such an outcome given the lack of clarity.

However, he declined to give details of the preparations other than saying: “The list is long. We’re a global company. We’re talking about people, customers, everything.”

Joussen said: “When you don’t know what is happening, you prepare for everything. Most likely it [a no-deal Brexit] won’t happen. That is what I believe.”

He added: “There are many maybes. I can only say profits are up. Let’s see what the remainder of the summer will do.”