Sales have picked up in recent weeks, boosted by heatwaves sweeping the whole country as summer sets in, the owner of Feichao ice factory, Sun Chao, told AFP.

Globally, heatwaves are becoming more frequent and intense because of climate change, experts say, and China is no exception -- 2024 was the country's hottest on record, and this year is also set to be a scorcher.

Last week, authorities warned of heat-related health risks across large swathes of eastern China, including Zhejiang province where Hangzhou is located.

"In the spring, autumn, and winter, a higher temperature of two to three degrees doesn't have a big impact on our sales," Sun said.

"But in the summer, when temperatures are slightly higher, it has a big impact."

Feichao is a relatively small facility that sells ice to markets, produce transporters, and event organisers.

As the mercury soared past 40 degrees Celsius (104 degrees Fahrenheit) in multiple cities across China recently, ice from businesses like Sun's was used to cool down huge outdoor venues.

In neighbouring Jiangsu province, organisers of a football match attended by over 60,000 people placed more than 10,000 large blocks of ice around the stadium, according to the state-owned Global Times.

- Extreme summers -

As AFP watched lorries being loaded with Feichao's ice on Wednesday, an employee from a nearby seafood shop came on foot to purchase two ice blocks -- each selling for around $3.50 -- hauling them off in a large plastic bag.

"In May and June, I can sell around 100 tonnes a day. In July, that number grows, and I can sell around 300 to 400 tonnes," Sun told AFP.

China has endured a string of extreme summers in recent years.

In June, authorities issued heat warnings in Beijing as temperatures in the capital rose to nearly 40 degrees Celsius, while state media said 102 weather stations across the country logged their hottest-ever June day.

The same month, six people were killed and more than 80,000 evacuated due to floods in southern Guizhou province.

China is the world's biggest emitter of the greenhouse gases that scientists generally agree are driving climate change and making extreme weather more intense and frequent.

It is also a global leader in renewable energy, adding capacity at a faster rate than any other country.