Sept 10 (Reuters) - Hurricane Irma knocked out power to over 1.3 million homes and businesses in south Florida on Sunday and threatened to leave millions more in the dark as it marched up the state's west coast through the rest of the day.
Irma crossed over the Florida Keys Sunday morning and was headed for the state's southwest coast with maximum sustained winds of 130 miles (215 kilometers) per hour, making it a dangerous Category 4 storm, the second worst on the Saffir-Simpson scale.
More than 1.3 million of its customers were already without power, said Florida Power & Light (FPL), the state's biggest utility.
On Friday, the utility warned Irma could impact around 4.1 million customers, but that was before the storm track shifted away from the eastern side of the state where FPL's customers are concentrated in Miami-Dade, Broward and Palm Beach counties.
Last October, Hurricane Matthew knocked out 1.2 million FPL customers as it skirted Florida's east coast without making landfall. Matthew did not come on shore and damage infrastructure, and it took the utility about two days to restore power.
FPL has warned customers to prepare for outages that could last weeks if Irma requires the utility to rebuild parts of its service territory.
FPL decided to shut only one of the two reactors at its Turkey Point nuclear plant on Saturday because the storm track shifted, and plans to leave both reactors at the St. Lucie plant in service because hurricane force winds are no longer expected to hit the sites.
FPL had said on Friday it planned to shut both units at Turkey Point sometime on Saturday about 24 hours before hurricane force winds reached the plant.
St. Lucie is located on a barrier island on the state's east coast, about 120 miles (193 km) north of Miami, while Turkey Point is about 30 miles south of Miami.
FPL is a unit of Florida energy company NextEra Energy Inc . (Reporting by Scott DiSavino in New York; Editing by Jeffrey Benkoe)