Many parts of Otago received their usual monthly amount of rain in 12 wet hours at the weekend, pushing Alexandra to possibly its wettest May ever, the MetService says.

The downpour, which started about 11pm on Saturday in most places and eased about 8am yesterday, caused slips, blocked drains, surface flooding and rivers to rise in the already wet eastern parts of the region.

The surface water had largely receded by mid-morning yesterday, and by late afternoon most rivers were dropping.

In Dunedin, the Fire Service was called to pump out several basements in Macandrew Bay and South Dunedin when culverts and drains overflowed.

Senior Sergeant Steve Aitken said that overnight, police dealt with a lot of surface flooding and overflowing drains.

Officers had helped to keep people safe from water on the roads by directing traffic, as well as helping cars out of a flooded road.

There were no big issues yesterday, Mr Aitken said. "It's stopped raining and everything's sort of calming down, but they're just cleaning up the mess now."

Across the harbour at St Leonards, Burkes Drive remained closed last night by a small slip, while nearby, a larger bank came down against the home of Lloyd Hiscock, stopping at his back door.

"I heard these thuds. After about the third thud, I got up to look and then there was this almighty bang."

The hill behind the house had collapsed, bringing down tonnes of sodden dirt against the back of Mr Hiscock's house. "I didn't sleep well after that."

Not only had it given his family a fright, it had them worried that more would come down, Mr Hiscock said.

Further south in Green Island, residents said water running off surrounding hills ran down driveways "like rivers" and flooded basements and garages.

In the Clutha district, heavy rain caused surface flooding that closed several rural roads around Milton and Balclutha, Constable Steve Griffiths said.

A slip on the Nugget Point Rd meant some tourists in campervans, who had stayed overnight at Nugget Pt, could not get out until the road was cleared in the afternoon.

Ten Otago rivers rose to their first flood warning level, prompting farmers in some areas to move stock, but most rivers had peaked and started dropping by about 2pm.

Alexandra's 67.3mm of rain in 24 hours was well above the May average of 23mm and exceeded the record of 46.5mm.