As the tail end of the polar blast makes its way across the South Island, the sewage systems of the mid Canterbury towns of Leeston and Tai Tapu have been flooded.
Selwyn District Council is asking residents of both towns to avoid using dishwashers, washing machines and taking showers or baths where possible to reduce the amount of water released into the wastewater systems.
Portaloos are being delivered to both areas so the system is not further overloaded.
And more fire crew have been brought into Leeston to help battle floodwaters threatening homes and shops.
Volunteer firefighters have been sandbagging in the town, where several houses and shops have been flooded.
Canterbury Area Commander, Dave Berry, says the 18-strong Leeston crew have been sent home to rest, and about 20 volunteers from Dunsandel, Darfield and Rolleston have arrived to help.
He says a 20-strong Civil Defence team is now taking over the sandbagging, freeing fire crew to respond to emergency calls.
"We've set up sandbags and booms around most of the town area, the shops. There is a set of pensioner flats that we've boomed off to reduce the water going there so those people can stay there. All round the town they're just sandbagging."
Dave Berry says the Leeston crew answered 50 calls for help on Saturday.
He says it will be a nervous evening with the rain not expected to ease until midnight Saturday.
And in Christchurch, the Avon and Heathcote Rivers are overflowing onto the road but traffic diversions are in place.
Fresh snowfall closing many highways
Snow has closed highways in the South Island.
State Highway 85 from Ranfurly to Palmerston is closed until at least midday Sunday.
Snow has also closed State Highway 87 from Kyeburn to Outram, and State Highway 80 from Glentanner to Mt Cook.
There are vehicle restrictions in place on Porters and Burkes Passes.
The Homer Tunnel to Milford Sound is closed until June 28 so staff can remove unstable rocks above the tunnel.
The Transport Agency is also urging caution on many central North Island highways due to snow.
There is snow on the Desert Road, and on other parts of State Highway 1, from Taihape north until just before Turangi.
Snow is also causing concern on State Highway 5 from Taupo to Napier, and State Highways 4 and 49 from National Park to Waiouru.
Caution is also advised on parts of State Highways 46, 47 and 48.
Sawyers Bay evacuees allowed home
Dunedin City Council says the residents of 11 homes evacuated overnight were cleared to return on Saturday afternoon.
Police moved Bell Gully residents at Sawyers Bay out at 4am Saturday after reports a two-day old slip was moving again.
The slip had already broken 30 metres of Upper Junction Road and threatened one house.
The council's roading maintenance engineer, Peter Standring, said council engineers had established the slip was not a threat to the Sawyers Bay homes.
More snow in mountains
Snow is falling again in the mountain passes of the South Island and has closed Porters Pass and Lindis Pass.
Lewis Pass is closed to towing vehicles or those without chains.
In Christchurch, Dyers Pass and Gebbies Pass in the Port Hills have closed as the snow returns once again.
Roading contractors are working hard to clear the main roads into Central Otago so trucks carrying much needed feed can reach farms that have been cut off for days.
State Highway 85 between Ranfurly and Palmerston remains closed due to snow.
New Zealand Transport Agency's Otago and Southland operations manager, Roger Bailey, says farmers are desperate for roads to open and he hopes that will happen on Saturday, although continued snow and hail makes the prospect less likely.
He says a 50 metre long slip over both sides of State Highway 1 north of Dunedin has been cleared but speed restrictions are still in place.