Flooding and extreme high temperatures have caused multiple deaths in eastern China as summer heat descends earlier than usual.

Record-high temperatures have been reported in Zhejiang province, east of the business hub of Shanghai, topping out above 42 degrees Celsius on Wednesday.

The neighbouring coastal provinces of Jiangsu and Fujian were also suffering under high heat, while Henan, Sichuan and Heilongjiang further inland saw many hospitalised for heat stroke.

The hot spell of the past 30 days has been described by Chinese weather watchers as widespread, prolonged and extreme and, due to higher demand for air-conditioning, the load on the power grids of seven provinces and regions has hit a record high, according to state media.

The hashtag #heatstroke was trending on social media with 2.45 million views on the Weibo platform, with discussions ranging from people being admitted to hospital to the detrimental effects of long-term heat exposure.

Floods have meanwhile struck much of the country, with three people reported killed and five missing in Sichuan province’s Pingwu county as of midday on Wednesday. One person was reported dead and eight missing in Heilongjiang in the northeast.

Experts say such extreme weather events are becoming more likely because of climate change. Warmer air can store more water, leading to bigger cloudbursts when it’s released.

Hundreds of thousands in south-central China have already been displaced by flooding. (Agencies)