Fifteen people have died of heatstroke in east China's Zhejiang Province due to a rare prolonged sweltering summer, local authorities said on Thursday.

With the 15 people dying between June 1 and Aug. 7, that figure is 3.75 times that of people who were killed by heatstroke in the province in the same period last year, statistics from the Zhejiang Provincial Center for Disease Control & Prevention showed.

The province has reported 2,082 heatstroke patients, including 288 serious cases, according to the center. The number of serious heatstroke cases rose 247 percent from last year.

As of Thursday, the province has seen 37 days with temperatures of more than 35 degrees Celsius. Record high temperatures were broken several times in Zhoushan, Fenghua and Hangzhou, the provincial capital. The highest temperature was 43.5 degrees Celsius in Fenghua City.

Prolonged scorching weather has swept many parts of east and central China. Heatstroke has left at least 10 people dead in Shanghai. Central China's Hunan Province and southwestern Chongqing Municipality have each reported three deaths from the condition.

Chinese meteorologists have attributed the extremely hot weather to a number of factors, including strong, stable subtropical high pressure, the absence of typhoons and global warming.