Predicting possibly the worst flood in Philadelphia history, Mayor Michael Nutter declared a state of emergency for the city Saturday afternoon.

The mayor cited potential 55 mph winds, a teeming Schuylkill River and potential large-scale power outages as reasons beyond the first state of emergency issued in Philadelphia since 1986.

"We've been through some tough times. We can do this," Nutter said at the city's Office of Emergency Management on Spring Garden Street.

Hurricane Irene should strike Philadelphia hardest between 4 a.m. and 8 a.m., the mayor said, and Gov. Corbett has put National Guard troops on standby.

The order gives police additional powers to close streets and arrest people out on the street, Nutter said. Also a Code Gray was issued, meaning, people can't stay out on the street Saturday night.

The mayor confirmed flooding reports already on I-76. Nutter also warned that if impacted, certain areas could have power outages from a week, to 10 days, to two weeks.

"This is one of the worst storm events to hit Philadelphia in the last 50 years," Nutter said.

Nutter told residents not in flood prone areas to stay at home. For others in flood areas, the mayor told people to leave home "right now" if they haven't already.