Crews are working to repair the break, at Hillview Avenue and Hanover Street, but the intersection is expected to remain closed for most of the day, according to police.
Further details were not immediately available.
Use Waze to navigate around the traffic near the intersection.
Mother Nature giveth... And man made water main taketh away. Showers in #PaloAlto earlier & water down the drain now pic.twitter.com/enqhoASlgs
— Matt Keller (@MattKellerABC7) October 16, 2015
Traffic Alert: Water main break closes Hillview Ave at Hanover St for most of day. Crews working to repair now. pic.twitter.com/E2FWf0lOVQ
— Palo Alto Police (@PaloAltoPolice) October 16, 2015