Houston — A massive water main break left parts of Houston looking like it did in the aftermath of Hurricane Harvey. The flooding closing a major freeway that circles the city where cars and trucks suddenly submerged. Drivers climbing atop their vehicles waiting for rescue.

Nobody expected this kind of flooding on a bright, sunny day.

The pipe that broke apart while undergoing repairs was 8 feet wide and supplies as much as 50% of the drinking water to the nation's fourth largest city.

Suddenly, across Houston, homes, businesses and the sprawling Texas Medical Center had low water pressure or no water at all. Schools dismissed early and early voting centers were forced to close.

A massive water main break is causing major flooding in east Houston, Texas, and water pressure problems all over the city. Many drivers were caught off-guard as the water rose quickly and some are stranded on tops of their cars. KHOU-TV

First responders used a high water rescue truck — last used during Harvey — to carry drivers to safety. With a major roadway shut down, traffic all over came to a standstill.

"I anticipate that you will have to boil water in the city of Houston for the next 24 hours if you are part of the Houston water system," said Houston Mayor Sylvester Turner.

This evening, city officials insist the water supply is safe, but they are urging people to boil tap water for the next 24 hours.