Thousands of people flocked to one of the world's largest indoor ski resorts in Shanghai, seeking to beat the heat as temperatures hit around 37 degrees Celsius in the mainland city.

Visitors snowboarded, skied and had snowball fights on Thursday on the slopes of the 98,000 square-metre Shanghai L+SNOW Indoor Skiing Theme Resort, where temperatures are maintained at five degrees or less all year round.

Tang Junqi was among those who spent the day there with her mother.

"It was so hot outside and feels like being in a pot. But it feels like in a fridge inside,” the 10-year-old said.

Shanghai on Friday experienced its 24th consecutive day of temperatures at 35 degrees or above in August, tying a heat run record that has stood since 1926.

The eastern city declared an orange alert, the second highest on its three-tier heatwave warning system, with high temperatures expected to continue for the rest of the month, according to the Shanghai Meteorological Bureau.

Scientists say extreme weather has been made increasingly likely by man-made climate change, caused by carbon emissions and exacerbated by energy-intensive activities, which include maintaining indoor temperatures at an artificially low level. (Reuters)