Kvas maker Deka said Thursday that it is selling three times the amount of the beverage in July as the worst heat wave in almost 40 years spreads across the country.

“We are selling triple the amounts of kvas this year compared with July sales in previous years,” said Deka, Russia’s second-largest maker of the traditional soft drink. Russian kvas sales will rise between 45 percent and 50 percent this year, compared with a 9 percent increase in 2009, it said.

A heat wave in the western part of Russia, the worst since 1972, will last another 10 days, the country’s chief forecaster said July 20. Temperatures have broken July records in dozens of cities in the region, including Kazan, Nizhny Novgorod and Samara, while Moscow may break its all-time record of 36.8 degrees Celsius this weekend.

Kvas is made from bread or malt and can be flavored with sugar, birch sap and fruit. It’s naturally bubbly and contains negligible amounts of alcohol.

Prices for rye and barley, used to make kvas, are rising as the drought curbs supply, Deka said.