A torrent of water sprayed from the road creating a geyser in downtown San Diego.
Footage, posted to Twitter/X, showed water shooting around 30ft into the air as cars drove past and onlookers filmed with their phones.
There was no immediate report from authorities about what had caused the leak.
It comes as Tropical Storm Hilary hits California, the first such weather event to hit the state in 84 years.
Millions of Americans were under flood and high-wind warnings as the storm moved north, unleashing heavy rains from the California-Mexico border to Las Vegas and beyond.
