The National Weather Service issued a flash flood emergency for Berkeley and Charleston Counties in South Carolina early Sunday.<br />Three people died on Friday and Saturday in traffic incidents in South Carolina, and a car passenger died in North Carolina on Thursday when a tree fell on Interstate 95, officials said.<br />The potentially historic precipitation will last all 48 hours of the weekend, due to a 1-2 punch from Hurricane Joaquin over the open Atlantic and a second weather system: Joaquin drenches the Northeast and a separate low-pressure rainmaker dumps on the Southeast.<br />President Barack Obama declared an emergency in South Carolina, authorizing federal aid, and parts of the state's coast braced for likely flooding with more than 15 inches of rain.<br />"What we're experiencing is an unprecedented event," said Mayor Joseph Riley Jr., referring to record rainfalls and extremely high tides happening at the same time, according to CNN affiliate WCBD .
