Shares in Thomas Cook plunged on Tuesday after the travel firm issued its second profits warning in two months, blaming a “disappointing” year on the prolonged summer heatwave across Europe.

Thomas Cook shares fell 29% to 34p, the lowest since 2012, after it said underlying profits for 2018 were now expected to be £250m – £30m lower than it was expecting two months ago.

In an unscheduled update two days before it publishes its audited results for the year to 30 September, the company also said it would not pay a dividend to shareholders.

It had already lowered its profit guidance in September, to £280m from £323m, blaming the hot weather which hit its UK business particularly hard.

The chief executive, Peter Fankhauser, said: “2018 was a disappointing year for Thomas Cook. After a good start to the year, we experienced a larger-than-anticipated decline in gross margin following the prolonged period of hot weather in our key summer trading period.

“From May to September the heatwave across Europe meant customers delayed booking trips abroad, leaving us with too much to sell in a heavily competitive market. The UK was particularly hard hit with very high levels of promotional activity coming on top of an already competitive market for holidays to Spain.”

Fankhauser said it was too early to say whether Brexit would have an impact on demand for Thomas Cook’s holidays, but said said bookings for summer 2019 were ahead of this time last year. “We are confident that our customers will still want to travel,” he said.

Revenue in the year to 30 September rose 6% to £9.6bn, but Thomas Cook said it was suspending its shareholder dividend for 2018, after paying out 0.6p per share in 2017.

Investors were also left concerned by net debt at Thomas Cook, which at £389m was far higher than the £267m predicted by City analysts, and made their previous expectation that the firm would eliminate debt by 2020 look unlikely.

Thomas Cook shares have had a turbulent run, falling from about 300p before the financial crisis to as low as 8p in 2011 before recovering some ground to a high of nearly 190p in 2014.

Hannah Maundrell, the editor-in-chief of Money.co.uk, said Thomas Cook would be hoping for cooler weather in summer 2019.

“Britons normally travel far and wide in seek of summer sunshine but this year it landed right on our doorstep meaning many of us put off the expensive summer holiday in favour of something cheaper and closer to home.

“Thomas Cook will be hoping for a long wet summer next year to buck this trend. If it’s anything like this year though the staycation will become more and more popular and people will opt to get their dose of sunshine a bit closer to home.”

The firm said its airline business grew in 2018 in the wake of the collapse of rivals including Monarch, and despite disruption caused by striking air traffic control workers in Europe.