Seen in this article from The Daily Mail, which spoke to photo hobbyist Phil McGrew:
The currency trader, who took up photography as a hobby two years ago, put his camera near his window as the rare thunderstorm lashed the city at 6pm.
He said: 'I moved from Fort Lauderdale, Florida to San Francisco about two years ago.
'We used to get a lot of big storms in Florida, but I've only seen them a couple of times here.
'When the thunder and lightning started last night, I thought I must get a picture of the lightning against the bridge.
My apartment looks out over Bay Bridge and I knew it would make a good shot if I could get it.'
Mr McGrew, who lives with his girlfriend Sherry, set up his camera on a long exposure for about 20 seconds.
Not realising he was about to take a once-in-a-lifetime picture, he perfectly captured the white flashes of light over the inky sky set against the golden glow of the bridge.