BEIJING—Several cities in China’s southern province Guangdong, a major manufacturing hub, have asked the industry to curb power use by suspending operations for hours or even days as high factory use combined with hot weather strain the region’s power system. The power restrictions are a double-whammy for manufacturers who have already been forced to lower production due to a recent surge in raw material prices including steel, aluminum, glass, and paper. Guangdong, an economic and export powerhouse with an annual gross domestic product equivalent to South Korea, has seen its electricity use surge 22.6 percent in April from COVID-hit 2020 levels, and 7.6 percent from the same period in 2019. “Due to the acceleration of economic activity resumption and persistent high temperatures, electricity consumption has been increasing,” said Guangdong provincial energy bureau last week, adding that average temperatures in May were 4 degree Celsius above normal, boosting air conditioner demand. …