Taipei, July 26 : A long-running heatwave in China has pushed electricity usage to record levels in some areas and led to blackouts, with warnings that the high temperatures are expected to continue for at least another week, a media report said. More than 300 cities were forecast to reach temperatures above 35 degrees Celsius on Tuesday. China Southern Power Grid Company said Monday's usage had surpassed last year's peak load by 3 per cent, The Guardian reported. The Guangdong province power grid also hit a record high, reaching 142m kilowatts, an increase of 4.89 per cent over last year's peak load. Blackouts were reported in the provincial capital, Guangzhou, which has recorded a full week of maximum temperatures above 37 degrees Celsius, including highs of 40 degrees Celsius on Sunday and Monday. Yang Lin, the manager of the company's dispatching office, said once temperatures in Guangzhou surpassed 35 degrees Celsius, every extra degree meant a corresponding load increase of 3m-5m kilowatts. The company said it was inspecting equipment to avoid overheating and malfunction, and pledged to maintain power supply. In recent years there have been widespread blackouts that have caused havoc across China, blamed on extreme temperatures, rising demand for electricity and shortages in coal, which is still the main source of China's power, The Guardian reported. China is among several countries to have moved back towards a coal-focused energy supply, despite ambitious emissions reduction pledges, amid a global crisis exacerbated by the Ukraine conflict. On Friday the ministry of emergency management warned safe operation of the power grid faced "severe tests". On Monday, 21 red warnings and 140 orange warnings were issued for high temperatures, predominately across the south-east and in the far west, including Xinjiang, The Guardian reported. /IANS