Fifty years ago, farmers in Italy's Emilia-Romagna region used to open the windows in their barns at night during the summer to keep their cattle cool.
Today, as heat waves send temperatures soaring to record highs, those windows stay open round the clock to protect the cows and ultimately their milk, the foundation of the area's centuries-old Parmigiano Reggiano cheese industry.
"Extreme heat impacts milk's quality and quantity," said Nicola Bertinelli, president of the Parmigiano Reggiano Consortium, who also runs the dairy farm that his family founded in 1895 on the outskirts of Parma.
With temperatures topping 40 degrees Celsius (104 degrees Fahrenheit), cows spend more time lying down, eat less and produce up to 10% less milk, one of the Parmigiano's only three ingredients alongside salt and rennet.
Production of authentic Parmigiano Reggiano is only allowed in five provinces, mostly in the Emilia-Romagna region and cows must be fed exclusively with grass and hay grown there.
"If it doesn't rain, grass doesn't grow, hay cannot be produced and it's impossible to obtain the milk needed to make the cheese," Bertinelli, 54, told Reuters.
He and others have also installed fans and water-mist systems, but those extra cooling measures have sent their energy costs soaring.
Rising bills are also hitting managers of the warehouses where cheese wheels are stored during the aging process for at least 12 months, sometimes three years or even longer.
More than 500,000 wheels of Parmigiano Reggiano, together worth more than €300 million ($343 million), are stored in the two warehouses operated by Credito Emiliano unit Magazzini Generali delle Tagliate (MGT) in the provinces of Reggio Emilia and Modena.
"During this year's peak heat waves, our daily energy consumption rose by about 30%," MGT director Giancarlo Ravanetti said.
"To make our facilities as energy-efficient as possible, we have improved our cooling systems and boilers, upgraded building insulation and increased renewable energy production," he added.
The region's climate-controlled warehouses have become institutions, collectively known as the Bank of Parmigiano. Behind their walls, technology and tradition go hand in hand.
Each wheel of Parmigiano Reggiano undergoes strict quality inspections - including X-ray scans - to rule out defects. The cheese is checked weekly by experts who tap each wheel with small hammers, listening for signs of flaws that may have developed during the ageing process.
"The human factor remains key and is the real strength of the entire process," Ravanetti said.
Paolo Ganzerli, international sales director at food group GranTerre, which posted consolidated revenue of 1.87 billion euros ($2.14 billion) in 2025, echoed Ravanetti's concerns about rising bills.
"If extreme events become longer-lasting and more intense, they will certainly have an impact on both the quantity and quality of milk, but above all they will lead to higher costs," he said.
There is a lot at stake.
The Parmigiano Reggiano industry generates an estimated 4.5 billion euros in revenue a year, employing thousands and powering the local economy.
In 2025, exports of the cheese accounted for more than 50% of Parmigiano Reggiano's global sales, with the United States as its largest foreign market.
Parmigiano Reggiano "has existed for more than 800 years," Ganzerli said.
"We don't want to be the last generation to eat it."
