The proclamation was originally declared a week ago by County Administrator Monica Nino.
The emergency status allows the county to be eligible for future disaster relief funding, should it be authorized by the federal and state government.
The proclamation was sent to Gov. Gavin Newsom and the State of California Office of Emergency Services so Contra Costa County can be added to the governor's statewide proclamation on Jan. 11.
Newsom issued the statewide emergency proclamation Jan. 4, allowing the state to make further requests for federal disaster assistance.
Contra Costa County board chairperson John Gioia said in a statement, "This local emergency proclamation will allow our county to access needed federal and state funds to help us recover from the extensive storm damage."
A series of atmospheric rivers has pounded the region since late December.
The severe storms have toppled trees, damaged roads, eroded creek banks, prompted mudslides and knocked out electrical power. The county said, with more rain likely on the way, residents are encouraged to prepare for the weather ahead by checking rain gutters and storm drains for blockage.