In a sign of the severity of this summer’s record heat, one of the two reactors at Connecticut’s only nuclear power plant has been shut down due to historically high water temperatures in Long Island Sound, source of the facility’s cooling water.

Unit 2 of Millstone Power Plant near New London was shut down Sunday afternoon after temperatures in the sound exceeded 75 degrees for 24 hours, the maximum temperature at which the nuclear power plant has permits to extract cooling water for the unit, said Ken Holt, spokesman for plant operator Dominion.

The outage in southeastern Connecticut appeared to have no immediate impact on power delivery, as the New England grid operator reported that the system operations were normal. New England