French wine makers are expected to produce nearly a third less wine this year than usual, after their vineyards were struck by frosts, poor weather and disease during the spring and summer. The country’s wine output is predicted to tumble by 29% this year compared with 2020, to the lowest level in decades, according to France’s agriculture ministry. Almost all of France’s wine-growing regions – including Bordeaux, Champagne and Languedoc-Roussillon – were affected by unseasonal spring frosts, which damaged grapes growing on the vine that had developed during a burst of warm weather. However, some areas were affected more than others. Production in the Champagne region, which includes its eponymous sparkling wine, is expected to plummet by 36% compared with last year, after frosts were followed by heavy summer rains which led to mildew fungus, a disease that causes the grapes and leaves to dry up. The Burgundy-Beaujolais region suffered severe damage from frost, hail and disease, and its total output is expected to fall by almost half compared with 2020. However, drinkers of French wine can breathe a sign of relief that 2021’s poor harvest is not expected to have an impact on supply to the wine market, thanks to reserves from previous years. “The spring frosts cut down a good part of the production, which will be historically low, below those of 1991 and 2017,” the agriculture ministry said in a statement, referring to two years when wine production was affected by severe spring frosts. The ministry forecasts production this year of 33.3m hectolitres, which would be 25% lower than average national output over the past five years. A hectolitre is equivalent to 100 litres, or about 133 normal-sized bottles of wine. French wine producers warned earlier in the summer that much of the grape harvest could be lost in the country, which is the world’s second-largest wine producer after Italy. In April, Julien Denormandie, France’s agriculture minister, described the devastation caused by freezing temperatures on vine and fruit crops as “probably the greatest agricultural catastrophe of the beginning of the 21st century”. The unseasonably bitter wave of cold weather raised concerns about the climate crisis, and the French government said at the time that the loss of a third of French wine production would cost almost €2bn (£1.7bn) in lost sales.