In San Francisco, PG&E says lightning blew out five separate transformers in Noe Valley causing a power outage overnight. The noise woke up several people in the neighborhood.
"It sounded like a big bomb going off. It was much larger than anything I had ever heard and I knew it had to be close," said San Francisco resident Julia Dawson.
"About one in the morning I was up watching TV and there was a large flash followed by a sonic boom that shook not only my house but several others on the block and it was quite frightening," said San Francisco resident Steve Rosasco.
Power was knocked out to about 100 customers.
"I think (the lightning) hit the line that these transformers were on and took them all out," said PG&E foreman Tony Damico.
The power came back on about 10:30 a.m.
The same system is bringing fresh snow to the Sierra. Drivers are being required to carry chains at Highway 50 at Meyers in South Lake Tahoe. Traffic on I-80 in Truckee is moving slowly due to snow and wet roads.
Mike Nicco is forecasting that showers and thunderstorms, with small hail, develop this afternoon and will linger through the overnight hours.