A MetService spokesman said a front was forecast to move slowly southwards over northern and central New Zealand today, bringing a broad band of rain with some heavy falls, and easterly to northeasterly gales.
An associated low to the west of the upper North Island would also move slowly southwards, then weaken and cross the South Island tomorrow.
North Otago could expect up to 130mm of rain between 6am today and 8am tomorrow, especially inland, with peak rates of up to 15mm per hour, he said.
Ashburton emergency management on standby
Parts of the Ashburton River could see flooding to levels seen in last week's storm, which caused the river bank to burst and a heavy rain warning south of the Rakaia River is set to continue until Wednesday.
Ashburton Mayor Neil Brown told Morning Report the council is keeping an eye on the situation and the emergency management system is on standby.
"We're ready to go if the weather gets progressively worse," he said.
"Overnight we've had about 20mm of rain in my rain gauge and it's been reasonably steady all night but just looking out of there now and listening to the rain on the roof it's looking to get heavier and heavier.
"The ground is really sodden and it can't go in so it'll run off to the lowest spot, which is the rivers."
Brown said he is expecting some, but minimal, damage to the river.
The stopbanks are fragile and were damaged in the rain last week. "Hopefully they'll hold up."
"There's one part of the river which is reasonably flat and there's a lot of shingle build up in there. In fact we've had some measurements done and there's a million cubic metres of shingle which needs to come out of the river."
The council needs government co-funding to remove the shingle, he said.
MORE FLOODING FOR CANTERBURY
Weather warnings are in place also for an already sodden Canterbury, with more flooding expected.
Heavy rain south of the Rakaia River is forecast from 2am today until 4am tomorrow, with 100mm to 130mm expected to accumulate about the foothills, and lesser amounts elsewhere, and heavy rain is also expected to continue falling in the region north of the river until midnight tonight, however this was expected to ease during the afternoon and evening.
ALPINE ROADS AFFECTED
South Island alpine passes were also in for another dose of snow and road snowfall warnings were in force.
Snow has shut off several roads in the Canterbury and West Coast areas.
The Lindis Pass (State Highway 8 - Omarama and Tarras) is closed due to heavy snow and up to 10cm was expected to accumulate above 800 metres, with lesser amounts lower down to 300 metres this morning.
Please use an alternate route or delay your journey, Waka Kotahi/NZ Transport Agency advised.
SH 8 Fairlie to Twizel is also closed due to snow, as is SH 73 Arthur's Pass to Otira and SH 73 Porters Pass (Springfield to Arthur's Pass).
Snow to 300 metres in the Mackenzie Basin is forecast.
The Crown Range, linking Queenstown and Wanaka, is open but between 10cm to 15cm of snow was forecast to accumulate above 800 metres with lesser amounts lower down to 300 metres until 3pm today.
Chains must be used between Eastburn Gates and Chainbay 1, a spokesman for the Queenstown Lakes District Council said this morning.
FLIGHTS CANCELLED
Meanwhile, two flights into Dunedin last night, from Christchurch and Wellington, were cancelled due to fog continuing to blanket the airport.
An early morning flight from Dunedin to Wellington today has been cancelled because the plane was unable to get to the city last night.
- John Lewis, ODT Online, RNZ
