The U.K. is experiencing its driest summer in fifty-seven years. It’s not been great. A British summer is usually a doubtful, fleeting thing. Sunshine and heat arrive in bursts from June until September, as if you were walking down a green-shaded path with occasional breaks in the canopy. When the sun does come out—during Wimbledon, say, or for a spell in August—British people go reliably mad, take their tops off, and barbecue frantically for a few days, until the skies cloud over again. This year hasn’t been like that. The country warmed up in June and has baked steadily since, like an oven that has reached its cooking temperature. Between late June and early July, Britain endured sixteen consecutive days when the temperature hit eighty-two degrees. Last month, eastern England had four per cent of its usual rainfall. In London, a city not known for its air-conditioning, the parks turned brown, the road surfaces went mushy in the afternoon ferment, and the nights became unbearably still. Foul, sweet smells hung in the air. This unusual British summer has been accompanied by terrible wildfires in California and Greece, a balmy Arctic, and dozens of heat-related deaths in Japan. Even when it finally rained, late last week, it didn’t bring much relief. Last Friday, Britain was hit by an estimated hundred and thirty thousand lightning bolts—enough electricity to boil a billion cups of tea—as summer storms played havoc with the nation’s roads, railways, and airports. August is going to be even hotter.

But at least the archeologists are happy. “It’s a bit like kids in a candy shop,” Robert Bewley, an aerial archeologist at the University of Oxford, told me, a few days ago. The freak conditions have made this summer one of the best in living memory for what archeologists call “parch marks”—ghostly, pale outlines of vanished castles, settlements, and burial sites that materialize on the land when it dries out and grass and crops die off. In recent weeks, archeologists in light aircraft, hobbyists with drones, and even people walking through their local parks have discovered Iron Age farms in South Wales, a Roman road passing near Basingstoke, burial mounds in Ireland, and the outline of Second World War bomb shelters on the lawns of Cambridge. Seen from above, the parch marks have a magical quality, as if a giant had doodled them from memory, but they are also disconcertingly real. They are only there because something else was.

Parch marks—and their less dramatic form, crop marks—are fairly common clues for archeologists who are working in places with long, dense histories of human habitation. (Bewley also works in North Africa and the Middle East.) The buried remains of Roman foundations or medieval walls will cause “negative” crop marks in a field of grass or wheat, because the roots of the plants on top of the ruins have less soil to work with—a phenomenon that becomes more noticeable when water is in short supply. The opposite is also true: filled-in ditches and moats, with their deeper soil, can lead to taller, greener plants and “positive” crop marks. The first aerial image to really excite British archeologists was taken in 1906, when British Army officers photographed Stonehenge from a balloon and noticed a darker ring of grass around the stones—the trace of an ancient ditch. “You go to a site to photograph what you know is there, and then you see something next to it,” Bewley told me. “That happens virtually every time we go flying.”

The last time the parch marks were so good—and Britain was so hot—was during the summer of 1976. Back then, water was rationed, and the country appointed a minister of drought. Newspaper photographers got hold of camels and marched them across dried-up riverbeds to make the English countryside look like Arabia. I was born in 1980, and have become accustomed, throughout my life, to people reminiscing about that Biblical summer whenever it looks like a British heat wave is going to last for longer than a weekend. I live in Bow, in East London, next door to an older couple, John and Francis, who drive a large black Rolls-Royce on Sundays and like to get away to Capri for some proper sunshine around this time of year. In early June, when the heat was getting serious, John stopped me in the street, his brow glistening, and said, “It’s going to be like 1976!” I waved him away. But he was right. In 1976, Bewley was twenty years old, studying archeology and learning to fly. He helped an excited professor catalogue the dizzying lines and circles appearing on the land. “There was film being thrown all over the aeroplane,” Bewley said. “It was unbelievable.”

Not all parch marks speak of ancient things. Last week, I took the train to Clumber Park, in Nottinghamshire, where the shape of a vanished mansion—complete with internal corridors and a sundial in the garden—reappeared in July. In 1707, Clumber Park was enclosed as a deer-hunting ground for Queen Anne, and for the following two centuries it was the home of the Dukes of Newcastle, a procession of politicians and gamblers. The thirty-eight-hundred-acre estate reached its height in the first half of the nineteenth century, under the fourth Duke, who planted the longest avenue of lime trees in Europe and kept a forty-ton frigate, the Lincoln, which he liked to sail on the park’s artificial lake. In 1838, the Duke spent three hundred and seventy thousand pounds—the equivalent of around forty million pounds today—to buy the Duke of Norfolk’s house, Worksop Manor, three miles away, and blow it up. His own seat, Clumber House, suffered two fires, in 1879 and 1912, and was demolished just before the Second World War. The park now belongs to the National Trust.

One sunny morning a few weeks ago, Ellen Ryan, Clumber Park’s collections officer, was opening the estate’s chapel for the day when she noticed the parch marks. “I just stopped,” she told me, “because you could see the mansion.” We were standing on a patch of dried-out turf where the great hall of Clumber House once stood. Pale, almost white traces in the fading grass showed where one corridor led off to the state drawing room, overlooking the lake, and another led to the kitchen and the servants’ realm of the house. Ryan, who was wearing dark glasses and a straw hat with little red and white flowers woven in it, gave me a guided tour. “Here we have the marble staircase, which went up either side,” she said, gesturing upward, “and then you come up to a gallery.”

After the fire in 1879, the seventh Duke, Henry Pelham Archibald Douglas Pelham-Clinton, rebuilt the house in the Italianate style. We passed through his prayer room and into his photographic studio. “I’ve got quite a fondness for the seventh Duke,” Ryan said. “He was a sweetheart.” The Duke was dropped as a baby and never grew properly. He had a leg amputated at the age of twelve. His wife, Kathleen, enjoyed breeding borzoi, a type of Russian wolfhound, and, between the two of them, they restored the estate to something like its former glory. In 1904, they employed thirty servants for the house, and a hundred and seventy for the grounds.