Federal defenders said they were flooded with calls from inmates this week as temperatures began to drop. “Our phone was ringing off the hook,” said the lead federal defender in Brooklyn, Deirdre von Dornum. She said inmates, using a dedicated line that connects the jail to federal defenders offices, had gathered around the telephones on their floors to report poor heating, little to no hot water and no lights in their cells.

On Thursday, Rachel Bass, a paralegal at the Brooklyn office of the federal defenders, said that she had fielded calls from about 15 inmates. “In the past hour I have gotten 11 calls,” she said. “People are frantic. They’re really, really scared. They don’t have extra blankets. They don’t have access to the commissary to buy an extra sweatshirt.”

She said many inmates complained of congestion and sore throats.

The president of the local chapter of the union, Anthony Sanon, said the problems began around Jan. 5 when the jail first lost power. The heating issues began last week, leaving inmates and staff to face freezing weather for the first time. “We didn’t have heat in the building, we didn’t have light,” Mr. Sanon said. “The weather was actually unbearable.”

The heat and power issues were unrelated, according to union leaders who spoke to facilities workers. The heating issues began when units that draw water up from the boilers froze. The workers said that the heat was on, but several units had been disabled.

The electrical problems originated in an electrical panel that blew out last month, the union leaders said. Although the panel was initially repaired, it caught fire on Sunday.

The jail switched over to emergency power, leaving the corridors lit only by dim lights, the cells dark and inmates confined to poorly heated cells during the coldest days of the winter so far. This week, the temperature plummeted to 2 degrees in New York City, as frigid weather swept over the Midwest and Northeast.

“The heat isn’t coming out properly,” Mr. Sanon said.

One inmate told a federal defender that a corrections officer had taken the temperature in a housing unit, which was warmer than the cells, and it was 34 degrees.