A lightning strike at 3:20 a.m. PT hit part of the power grid feeding the North Thompson Valley, B.C. Hydro spokesman Dag Sharman said.
Power is out from a point 20 kilometres north of Kamloops all the way to Valemount, roughly 300 kilometres north.
Sharman said hydro crews have to rebuild a transmission tower before the line can be re-energized.
Power isn't expected to be restored until at least noon Monday, he said.