BARTON, Vt. — About 1,500 households in northeastern Vermont lost power overnight as temperatures dipped to about 20 below zero and municipal buildings in two towns offered shelter Sunday for those needing to get warm.

Vermont Electric Power Cooperative said the early morning outage was caused by a broken transmission pole possibly from the extreme cold. Municipal buildings in Barton and Orleans opened for people needing warmth.

Residents of the rural Northeast Kingdom tend to have backup sources of heat such as generators and wood heat. But an emergency generator didn’t kick in for Sheffield Selectboard Chairman Walter Smith, who said he lost a greenhouse full of about 500 orchids.

“I’ve got it working now, but it’s too late,” he said around midday on Sunday.

Bruce Urie, chairman of the selectboard in Craftsbury, said his generator didn’t start up after the power went out around 3 a.m.

“It was a really bad night to have the power go off with the temperature being what it was,” he said. He has backup propane heat in his house and eventually got the generator going.

The outage also affected customers in Albany, Barton, Glover, Greensboro, Irasburg and Wheelock.

VEC said repairs took longer than expected because of complications from the cold temperature. Most customers had their power restored by about 3:30 p.m.