“I’ve lost nearly 50% of my harvest this year and it could go up to 70%,” he said. “It’s gone. Everything has dried up. Since I started farming this land after the end of communist rule, I’ve never seen a catastrophe like this.”

Somogyi said the unprecedented crisis did not come out of nowhere, and that the heatwaves and droughts of previous years had already offered a warning. Scientists say that human-caused climate breakdown is making every heatwave in the world more intense and more likely to happen.

“You could see this coming,” he said. “The harvest was already poor last year. But we were lucky because the Danube stayed high. Despite the intense heat, there was still enough water in the soil. This time, there is no hope of saving our crops.”

On the near-deserted roads running alongside the river, families with children sought relief in the Danube’s shallow waters, while, not far away, military water tankers were siphoning water from rural wells, hauling vital supplies to the storage pools that feed the local grid.

Szentendre

Across the river from Pócsmegyer, on the opposite bank of the Danube, lies Szentendre, a town known for its community of artists. During the most intense days of the heatwave, some evening performances have been held by candlelight in an effort to reduce electricity consumption.

Here, in recent weeks, vast, desert-like islands have emerged. The exposed riverbed is cracked like a mosaic of hard, dry clay, baked by suffocating heat that has pushed temperatures in Budapest close to 42C, with overnight temperatures hitting a high of 28C. Europe is warming faster than any other continent, with intense summer heat and prolonged drought being amplified by the deepening human-caused climate crisis. Extreme conditions continue to fuel wildfires and strain water supplies.

In some stretches of the Danube near Szentendre, it is now possible to walk through it with the water barely reaching above your ankles.

“Swimming and navigation are banned here,” said László Balázs, 44, head of the local river rescue service. “But people escaping the heat still enter the water, unaware it can suddenly drop into deep pools where they risk drowning.”

At the end of June, Budapest police (BRFK) said three people had gone missing in the Danube over a single weekend. Water police later recovered one body near Iváncsa, while searches continued downstream for the other two missing swimmers.

The drought and resulting disruption to energy supplies have also left some Hungarian towns struggling with shortages of drinking water. In a room inside Szentendre’s tourist information office, thousands of bottles of water are stored ready to be distributed, particularly to elderly and vulnerable residents.

“About 4,000 to 5,000 households were left without water,” said József Gulyás, 62, Szentendre’s deputy mayor. “We distributed 25 tonnes of water and received about 100 emergency calls a day. We had never experienced anything so serious. Elderly women would hug the officers delivering water and burst into tears.”

Budapest

Driving from north to south, towards the Hungarian capital, Budapest, where the level of the Danube under normal conditions reaches an average height of 2 to 3 metres, and can rise as high as 8 metres, intense summer heat and continuing drought conditions caused the river to fall to a record low of just 14-19 cm on 4 August.

The water levels have fallen so dramatically that, as the Danube has retreated, it has revealed a succession of relics long hidden beneath its waters, including the remains of a woolly mammoth, a bridge destroyed after the second world war in Budapest, a Nazi warship and an unexploded British bomb.

The water is so low in the capital that on 28 July, at about 4.30pm, Gábor Kürti, president of the Magyar Kerékpárosklub (Hungarian cyclists’ club) and owner of a cargo bike company, left his office in central Budapest, jumped on his bicycle and, in an unprecedented feat, rode for 30km along the exposed bed of the Danube, with his journey quickly going viral on social media.

“I wanted to show that if you can cycle along the bed of the Danube for 30km, it means that, because of this climate emergency, we have literally hit rock bottom,” he told the Guardian.

Riding his KTM X-Strada 20 gravel bike, Kürti set off from the mouth of the Szilas stream (Szilas-patak) and made his way across fine gravel, large pebbles, hard-packed sand and mud, eventually reaching the ferry terminal at Vác about three hours later.

“For many people it was an extraordinary adventure. For me, it was heartbreaking,” he said. “Cycling through parts of the river where, as a child, I used to swim or go kayaking, and which I could now cross on a bicycle, filled me with an indescribable sadness. It was like looking at the scene of a terrible accident. Throughout that journey, the scale of the catastrophe was unfolding before my eyes.”

Nagytétény

Kürti took the Guardian into what, until only a few months ago, was the striking floodplain forest in Nagytétény named Kis-Háros-sziget, a protected area home to climbing plants, wild vines and several families of European beavers.

The river is reached by walking across ground that would normally lie several metres beneath the water. Here, one branch of the Danube has receded so dramatically that it came to an abrupt halt, blocked by an exposed riverbed left behind by the drought.

Its dry, clay-like surface looks like an image from a future shaped by the escalating human-caused climate crisis. Yet this is happening now. Passersby walk across what was once the river, their feet sinking into patches of mud. Kayakers struggle to make their way through the remaining shallow channels; many eventually give up, lift their kayaks on to their shoulders and walk home.

Hungarian authorities have been pumping water into large areas of the country’s nature reserves such as the one in Nagytétény, to keep marshlands from drying out as the drought intensifies.

Paks

Continuing south, the road finally reaches Paks, home to Hungary’s nuclear power plant, its towers rising above the horizon. Here, municipal workers have been working weekends to keep more than 700 threatened trees alive and water the town’s flowerbeds.

“I’ve been doing this job for 18 years,” said Szilvia Farkas, 39, who is employed by Dunakom Zrt in Paks, owned entirely by the municipality, to plant and water trees and plants. “I have never seen so much vegetation dry out in all my years doing this job, and I have never worked as hard as I have this year to try to keep it alive.”

Dunakom Zrt uses its own drilled well for water extraction. In addition, the company is able to extract water from a decantation basin. The public is not permitted to use tap water for irrigation at the moment; instead, residents collect greywater and use it to water their gardens.

In the country’s more marginalised and deprived areas, the water crisis has compounded longstanding problems for thousands of people who were already living in difficult conditions before the drought, struggling with inadequate access to running water and sewage systems.

Géza Orsós Renáta, 43, who lives with her four children in a small farmhouse on the outskirts of Paks, has never had access to running water. Orsós, who also works for Dunakom Zrt, helping to water public green spaces drying out in the heat, has long relied on water from a neighbour.

“Even in winter, we have to pump water and heat it in large bowls so we can wash,” she said. “Now a friend brings us water once a week. But it is becoming unbearable.”

Driving back from Paks, tall, swollen clouds occasionally gather on the horizon in the clear skies above Budapest, appearing to promise the return of rain, only to fade by evening, dashing the hopes of an entire country.

For now, people can do little but cling to the hope that the Rock of Starvation will disappear once more beneath the currents of the Danube, returning to the depths of the river and becoming little more than a legend again.

But Somogyi, who grew up hearing the story of the boulder passed down through generations, and who is now witnessing the consequences of the warning it was said to foretell, knows it will not.

“The drought will return next year,” he said. “That is the trend. And there isn’t much that we can do.”