MetService has an orange heavy rain warning in effect for Dunedin, North Otago and Clutha. It signalled that people should expect 80mm-110mm of rain about the ranges, and 50mm-80mm nearer the coast from noon today to noon tomorrow.
There were peak rates of between 5mm and 10mm per hour expected, with 15mm per hour possible in the ranges.
"Further rain is possible for Clutha and Dunedin during tomorrow afternoon and evening, with a low chance of upgrading to a red warning."
Dunedin Mayor Jules Radich said the council was prepared for the rain.
"The rain overnight was not too bad, there are crews on standby for later this afternoon, they were stood down last night.
"From midday today until midday tomorrow is the danger period and there are some spots with quite high rainfall predicted."
A localised downpour could cause problems, but drains had been cleared, Radich said
There was a sandbag centre in town if people felt they needed them, he said.
"We're as ready as we can be.
"I don't think our rivers will have too much trouble with this, speaking optimistically."
The council this morning said contractors were out and asked people to help by clearing gutters if possible and leaving debris on kerbs for collection.
Meanwhile, snow has been falling in parts of the South overnight.
Webcams show snow on the Crown Range Road and the Lindis Pass (State Highway 8) this morning. Both roads remain open, and earlier road snow warnings have been lifted.
All main highways in the South remain open this morning.
The Central Otago District Council says surface flooding has been reported around the Ida Valley area and crews are out monitoring the situation. Auripo Rd is closed between Boundary and Thurlow Rds due to flooding.
Emergency Management Otago stakeholder engagement adviser Erica Andrews earlier said it was monitoring the rainfall situation.
"Streams and rivers may rise rapidly, while there’s likely to be surface flooding, slips, and difficult driving conditions."
Niwa forecaster Seth Carrier said the heavy rain would affect much of the country today.
The agency yesterday said up to two months' worth of rainfall could hit in parts eastern Otago.
MetService forecaster Mickey Malivuk said with grounds already saturated, the situation was "interesting".
"We’ve got a band of rain moving slowly eastwards, but it’s likely to hang around in the eastern areas of Otago and the South longer than usual. It’s going to be quite a lot of rain for that region."
The North Island has also been hit by the wild weather.
Coromandel and the Bay of Plenty had the worst of conditions overnight, MetService Duty forecaster Heath Gullery said.
About 100 homes in Whitianga were without power this morning, with reports of surface flooding and debris on roads in the area.
Taranki had 100-150mm of rain, while Tasman had up to 250mm in some areas.
MetService's rain radar showed the rain band moving across the upper North Island and the centre of the country early Thursday morning.
MetService meteorologist John Law said the "band of rain" was likely to be stuck over the country for a few days.
The wet weather was taking its time moving on from Coromandel and Bay of Plenty but in general things would clear up in the North Island during Thursday, he said.
However, things would ramp up in the southeast of the South Island, Law said.
"It's an incredibly wet situation down across the likes of Otago."
- additional reporting RNZ/ODT Online
