A flood warning has been issued for Suffolk, Franklin, and Isle of Wight and Southampton counties because of the risk of the Blackwater River overflowing.

The National Weather Service in Wakefield is urging residents to use extreme caution near the river. People should move to higher ground immediately if they see rising waters.

The river had reached flood stage (12 feet) by 9:45 p.m. Friday, the weather service said. The flood warning states the river could rise near 14.7 feet by Sunday evening — a lower prediction than the earlier 15.2 feet. At 16 feet, moderate flooding and limited access to nearby buildings could result. The warning will continue until further notice is issued.

The river’s previous crest was at 15.3 feet on Feb. 7, 1998, the weather service said.