WARSAW - A heatwave has forced Poland to sharply cut electricity supply to industry for the first time in over a decade, pushing some companies to limit production.Prime Minister Ewa Kopacz called the situation "very serious" as weather forecasts for the coming days showed high temperatures will persist. She added that currently she saw no risk of limiting energy consumption for households.Europe's second largest copper miner, Poland's KGHM , warned it might have to curb output. The local unit of the world's largest steel maker ArcelorMittal halted some of its operations.The heatwave and lack of rain cut the amount of water needed to cool coal-fired power plants, from which Poland generates about 90 percent of its electricity. The country has virtually no solar energy generating capacity.Temperatures in Poland topped 30 degrees Celsius last week and may reach 39 degrees this week, according to Poland's meteorology institute.The national grid operator Polskie Sieci Elektroenergetyczne (PSE) introduced the sharpest possible limit on energy consumption for large energy consumers - in excess of 300kW."This is an extreme phenomenon," PSE's head Henryk Majszczak said. "We are recording high air temperatures and a lack of wind, which could be used by wind farms."PSE said the limits on energy consumption will be in place from 0800 GMT to 2000 GMT on Monday. Last week, PSE said that if continued, the heatwave may put its operations at risk.