Service is back on at Hackensack-Meridian Raritan Bay Medical Center, but power outages did affect operations.
Administrators say they were forced to use backup generators, and patients arriving by ambulance were sent to other hospitals.
Emergency surgeries could not be performed and three pregnant women were transferred in case they needed a C-section.
As of Sunday morning, patients were still being diverted in some cases.
Rooms were being cleaned and sterilized again as temperatures stabilized.