SAN FRANCISCO -- An especially powerful squall line that passed over the Bay Area Monday afternoon prompted a National Weather Service flood advisory as heavy rains forced street and freeway on-ramp closures and temporarily halted Muni service in downtown SF.

Behind San Francisco's Moscone Center at 4 p.m., there was so much water in underground storm drains that it caused a geyser-like effect, forced rainwater upwards through openings in the streets and sidewalks.

On the roads, sheets of rain lashed unsuspecting motorists and flooded streets and freeways around the Bay Area.

So much rain fell in such a short time, many storm drains couldn't handle the volume of water and drivers had to navigate standing water and flooded roads.

In San Francisco on Folsom Street between 17th and 18th, residents were on edge after the downpour caused sewage lines to back up and flood their street.

On Monday evening, the Red Cross went door-to-door to make sure ground floor apartments were sanitary and safe. Everyone KTVU spoke with said they were shocked that such a short downpour could produce so much rain and wreak so much havoc.

San Francisco firefighters had to be hosed off by hazmat crews after working in raw sewage late Monday afternoon.

Residents were warned to leave their walking shoes outside

“I knew it was going to rain, but I didn't know this was going to happen,” said area resident Cristiana Seppas

The sudden downpour left many Bay Area roadways flooded, particularly in San Francisco, California Highway Patrol Officer Scott Cakebread said.

Several on-ramps to Interstate Highway 280 were closed for a period of time, including the Mariposa Street, Sixth Street and King Street on-ramps. The on-ramps were reportedly reopened at around 5:30 p.m.

Cakebread said westbound Interstate Highway 80 near Gilman Street in Berkeley is particularly susceptible to flooding, as are portions of Interstate Highways 880 and 980 in Oakland.

"They've just had flooding all over the place," he said. Flooding shut down southbound I-280 between 6th Street and Highway 101. Across the Bay Area, high water slowed traffic to a crawl

CHP said the number of calls for service tripled during the downpour.

"There was a time period between 2 p.m. and 4 p.m. when we took approximately 750 calls for service,: said CHP spokesman Trent Cross. "Typically during that same time period on a dry day, we're looking at maybe 250 calls."

But the problems didn't end when the rain stopped.

Rushing water forced the temporary closure of the Van Ness Muni station and suspended rail service from Embarcadero to West Portal for hours.

“Market Street itself was like a river,” said Muni spokesman Judson True “The cars were at least up past the middle of the wheels.”

In Oakland, fire crews assisted by bystanders swept water out of a building housing condos and a ground level restaurant with squeegees and brooms.

"The cap on the storm drain popped due to pressure and it exploded,” said Oakland resident Jesse Branstetter. “We basically had Niagara Falls coming into our patio and [it] filled our dining room.”

Oakland hills resident John Murrell raced for sandbags to keep his home from flooding

Everything coming down the street was running down the side of my house, which is very bad,” explained Murrell.

Murrell said he's lived in the Bay Area for thirty years and he's never seen a downpour like Monday’s deluge.

“We've had rain before that is extremely heavy, but this is probably the worst I've ever seen,” said Murrell.

Back in the mission, the Red Cross said it will continue to keep an eye on the area. Residents told KTVU the area is prone to flooding, but they can't remember the last time they considered evacuating.