A flood warning is in force in Otago as rivers continue to rise after heavy rain.

Houses have been flooded and roads closed by slips.

Rain in the Manuherikia, Pomahaka, Taieri, Kakanui and Shag catchments has caused rivers to swell up quickly.

People are being advised to be mindful of the conditions, and watch for rising water.

Senior Sergeant Steve Aitken told NZPA police had a busy time dealing with a number of incidents overnight.

Portobello Road between Dunedin and Macandrew Bay was closed, as well as Burkes Drive, Highcliff Road, and Scroggs Hill Road.

"A bank has come down against a house in St Leonards and there's also been a lot of surface flooding and overflowing drains," Mr Aitken said.

The Fire Service has also been kept busy, St Kilda fire station officer Howard Weir, said.

"When Dunedin gets a period of rain like this there's always certain low-lying areas in south Dunedin that have the same problem time after time so we've had a few of them.

"There have been issues with blocked culverts on Portobello Road and water spilling out where it shouldn't go.

"We've also had to pump water out of the basements of several homes in the Macandrew Bay area, which was the result of a blocked culvert which couldn't drain properly. There's only so much you can do because we haven't got the expertise or the machinery to unblock culverts, we can just try to help as much as we can, but essentially it's a council issue," he said.

Mr Weir said the forecast was for to rain to ease during the day.

"I think everyone's got their fingers crossed for that."

Yesterday, a sharp, torrential downpour forced some Auckland residents from their homes.

About 15 frightened residents in Mt Roskill, Hillsborough and Mt Eden called emergency services between midnight and 3.30am as rain and sewage gushed into their homes and garages.

According to the Metservice's nearest gauge at Mangere, 26mm of rain fell in just one hour, between 2am and 3am.

Auckland civil defence controller Clive Manley said the council supported the Fire Service by sending out contractors in a suction truck to clear gully traps.

Mt Roskill landlord Jonathan Baker said his tenants evacuated their one-bedroom Parau St home and slept on his lounge floor, after the flash flood caused a sewage and drain line to overflow.

"It was a terrible night ... and that's the second time it's happened," Baker said.

"It was because of the antiquated council's combined sewer and storm water line. It's absolutely disgusting."

Tenant Toshi Nakama, of Japan, said he spent about three hours trying to save his possessions from the dirty water.

"Almost everything [was damaged], just not the laptops. It's lucky we have internet so we are looking for a place to stay tonight. Maybe a backpackers'."

One street over in Akarana Ave, Isope Wolfgramm struggled to move his 90-year-old disabled mother.

As water rushed into their home, which he had owned for 22 years, he put his mother in a wheelchair and carried her upstairs.

Wolfgramm said the ankle-deep water filled their downstairs area within minutes.

"I was sitting here [in the lounge] and all of a sudden I felt this water underneath me, water flushed in."

The carpets were water-logged and the house smelled damp yesterday, but the family said they would not be forced from their home.

"It's not going to be liveable for a few days, but we'll all move upstairs," said Wolfgramm.

Graham Syder, the owner of Studio of Tablewear, was devastated to be cleaning out his flooded stock room for the second time in two weeks.

"We only just finished the assessment for the last one yesterday. There was maybe $50,000 of stock damaged and a huge amount of computers, about $17,000," said Syder. "It's pretty upsetting."

Syder, who has owned the shop for more than six years, believed a blocked drain on Mt Eden Rd was causing the rainwater to spill into his stock room.

Mt Roskill fire station officer Terry Bird said they weren't able to clear water from the houses because of blocked drains.

"The rain was very heavy for a period and the drains couldn't cope, the water wasn't draining away so it was causing ponds," Bird said.