Extreme heat in Europe is testing the assumption that hot summers mean a boost in sales of alcohol, with studies showing drinkers less inclined to reach for a chilled beer or Aperol Spritz when it gets too hot.

Alcohol sales on average rise with temperature up to just over 32 degrees Celsius, after which the positive effect becomes smaller, researchers from the University of California, ETH Zurich and North Carolina State University found.

The effect varied by geography and was less pronounced in already warm regions, said the March research paper, which was based on U.S. retail sales data between 2006 and 2023.

"Generally warm weather is good for consumption. But there is also an upper limit ... beyond which it's just uncomfortably hot," said Marten Lodewijks, president of drinks market research firm IWSR, adding this reverses the trend for some drinkers. Europe's summer heatwave, which began on June 20, was the most intense recorded on the continent, causing thousands of excess deaths and overwhelming healthcare systems, disrupting power generation and damaging infrastructure. European health authorities said people should avoid alcohol, which increases dehydration and body heat. Its consumption and sales in stores were briefly banned in Paris.

"There is an important difference between warm weather and extreme heat," said Carlsberg's global director of public affairs Kristian Henningsen, adding that extreme heat can push people to stay inside rather than go out for a drink.

The Danish brewer is focused on offering drinkers more choices, such as low- and no-alcohol beers or soft drinks, partly to adapt to such changes, Henningsen told Reuters.

Other major beer and spirits makers either declined to comment or did not respond to requests for comment on the likely effects of more extreme weather on their business.

'Docile, tired, not with it'

Top brewers such as Anheuser-Busch InBev have previously blamed unseasonably cold or wet weather for disappointing earnings during the summer, when drinkers have normally turned to chilled, lighter drinks such as beer.

Another major beer maker told Reuters that weather is one of the main metrics it considers when forecasting beer sales.

David Lambert, a 59-year-old parish priest in London, said he was less inclined to reach for an alcoholic drink during Britain's recent extreme weather when temperatures hit a record-breaking 37.7 ​degrees Celsius in Norfolk, ​eastern England.

"I certainly didn't drink as much alcohol last week. You can't... It just makes you docile, tired, not with it," Lambert told Reuters at London's The Sun Wharf.

Bar staff at the JD Wetherspoon pub were busier than usual during the heatwave, shift leader Yash Hitesh Hansora told Reuters, with drinkers who initially sought outdoor space, which The Sun Wharf does not offer, soon asking for air-con and ice.

Spiros Malandrakis, global insights manager for alcoholic drinks at Euromonitor International, said more extreme heat could have mixed effects for those in the drinks trade.

As well as pushing some to drink less, heatwaves can hurt economies and spending power and hit agriculture, increasing alcohol production costs, he said.

Malandrakis also predicted some people will drink more in a world that "feels like it's literally on fire". The EU's Copernicus Climate Change Service said heatwaves will become more frequent and intense, while scientists said Europe's heatwave would have been virtually impossible without human-caused climate change, which is warming it at a faster rate than any other continent.

For some, the heat is still the perfect excuse for a drink.

"There's just something about the sunshine that makes you want to pour a glass of wine," said Teresa Angell, a 57-year-old working in billing support in London.