Rain has eased in Dunedin and "the city has come off OK" but surface flooding is still widespread.
The forecast overnight for the area is for a low level of rain, which should help receding floodwaters.
Dunedin's mayor Dave Cull said council and civil defence staff will remain on "a heightened state of alert" this evening, before pursuing a clean up in the morning.
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"The heavy downpours that were predicted happened about 4pm and have started easing off. On the whole we expect things to continue to improve, expect perhaps around some of the rivers."
The Taieri River was continuing to rise, Cull said. Residents in Middlemarch and Henley had been particularly affected by floodwaters.
"There will be a few people that are a bit uncomfortable, that have had to leave their homes but overall the city has come off OK."
It had not been necessary to declare a state of emergency, Cull said. However, he expressed some concern about the city's ability to cope as severe weather events become more commonplace.
"Clearly our infrastructure was not designed for this intensity. The volume, if it's spread out over time, is manageable."
EVACUATIONS, ROADS FLOODED
Dunedin residents were still urged to stay off the roads where possible in the city and the Taieri Plain.
Earlier, one person was freed from a car after it became stuck in floodwaters near Kaitangata in South Otago. Police were alerted about 4.50pm near the intersection of Lakeside and Stations Rd, Lovells Flat, between Balclutha and Kaitangata. The man was under a train overpass when he ran into trouble. He was rescued uninjured.
Most highways were open on Tuesday afternoon, but many warnings were in place, a NZ Transport Agency spokeswoman said. One road in the South Island was closed on Tuesday afternoon – State Highway 90 from Raes Junction to Tapanui – because part of the road had dropped out. SH8 from Roxburgh to Millers Flat was closed in the morning due to flooding but reopened about midday.
State Highway 1 south of Milton had not closed Tuesday afternoon as was initially advised by the police, but as of Tuesday evening was closed to cars with only four-wheel-drive vehicles allowed access, because of extensive flooding between Milton and Balclutha. There were warnings for other Otago highways due to slips, strong winds or surface water.
Dunedin City Council Civil Defence Controller Sandy Graham said widespread surface flooding was still present around the city overnight on Tuesday and people should avoid non-essential travel.
"Not all flooding is signposted. If you need to drive, please reduce your speed through flooded areas so water isn't pushed into properties."
Henley residents had earlier been door-knocked by police and advised to evacuate as rain fell. Meanwhile, all Dunedin residents were urged to cut back on showers and use of washing machines, as continued rain had put pressure on wastewater pipes and pumping stations around the waterlogged city.
Mosgiel and South Dunedin residents concerned over flooding or who have had issues could still collect sandbags overnight from various sites, including Memorial Park and Hotel Taieri car park, Mosgiel, and Ice Stadium car park, Dunedin.
Three streets in Middlemarch, Otago, were earlier closed due to surging from the wastewater network. A pump was being used to provide extra capacity while the area was hit by heavy rain, a Dunedin City Council spokeswoman said.
WETTEST DAY OF THE MONTH
MetService Meteorologist Andrew James said Dunedin had experienced its wettest day of the month with 47.7 millimetres of rain falling, with a peak hourly total of 10.6mm.
"When we talk about heavy rain it's around 6.5mm per hour, so today was really wet for Dunedin," said James.
The low pressure to the north of Dunedin is moving away, however it is expected to remain windy overnight, particularly by the coast.
Otago Regional Council opened the Riverside spillway gates on the Taieri River at Outramon Tuesday afternoon to divert water into a ponding area that is part of the lower Taieri Flood Protection Scheme to reduce the effects of flooding on properties further down the river at Henley.
Director of science, hazards and engineering, Dr Gavin Palmer, said river levels continue to be monitored around Otago. "At the moment there is no spill from Silver Stream, which is positive. We'll keep an eye on this because even though it's dropped, it's sensitive to rainfall.
"We're also monitoring the Mill Creek pump station, which came under pressure during the July 2017 floods and have brought in extra materials to stabilise it if needed, although we don't anticipate any issues," Palmer said.
Dunedin rivers are also being monitored, especially the Water of Leith near Leith Street Central, and Lindsay Creek at North Road.
FLOODING IN SOUTHLAND, SNOW IN CANTERBURY
Further south, some schools were closed in northern Southland and west and south Otago. Blue Mountain College in Tapanui remained open but pupils sitting public exams were warned only to travel to school if they could in safety.
The New Zealand Qualifications Authority (NZQA) says students who can't attend their exams due to the weather won't be disadvantaged.
More than 30,000 students across the country have exams scheduled on Wednesday. Derived grades will be offered to students who can't get to their exams because of flooding, snow or road closures. "Students spend many hours preparing for exams, so we do our best to ensure exam centres are open should students be able to get there safely," NZQA deputy chief executive Grant Klinkum said.
On Tuesday night, The Bruce ward Civil Defence team at Milton were playing a waiting game after the storm caused isolated flooding throughout the South Otago town.
Milton volunteer fire brigade deputy chief and civil defence team member Warren Tait said they had "about five call outs from 4pm as the situation worsened. People were sandbagging their back doors". A couple of houses were at risk, he said.
On the main street, the flood-prone Tokomairiro Community Hub had been sandbagged and cordoned off. Civil defence team member Jill McIntosh said there had been a steady stream of people into the Clutha District Council service centre asking for sandbags and to report that their toilets had backed up.
Team co-ordinater Allan Philips said he would be assessing weather and flood water levels Tuesday evening and Wednesday morning. Emergency centres had been set up and would remain open in Balclutha and Lawrence until the situation could be reassessed.
Environment Southland had earlier activated flood warnings, and the Clutha District Council issued a warning to users on the Tuapeka West, Glenkenich and North Richardson rural water schemes to boil water till further notice due to wide-spread rain and flooding.
Earlier in the day, at about lunchtime on Tuesday, much of the rain was concentrated on the Canterbury region. MetService also received a report of a good amount of snow during the morning from Castle Hill Village, inland from Christchurch on the western side of Porters Pass. There were also reports of snow from Ranfurly and Roxburgh in Central Otago.
MetService meteorologist Lisa Murray said a slow moving low was lying to the east of the country, just south of Banks Peninsula. "It's clockwise around a low, so the onshore flow into the lower half of the South Island is either southeast or southerly. That's why it's feeling quite cold down there."
At Le Bons Bay on Banks Peninsula, the lunchtime temperature was down to 4.3 degrees Celsius, with the area being buffeted by a cold southwest wind. In the 12 hours from midnight to midday, Methven recorded 32.8mm of rain, Timaru Airport had 22.6mm, Mt Cook Village had about 20mm and Ashburton had 18.8mm, Murray said.
THUNDER, WATERSPOUTS FOR NORTH ISLAND
In the North Island, there had been some thunderstorms in Northland, Auckland and northern Waikato.
Waterspouts and lightning were also seen off the coast of an Auckland beach, near Torbay on the North Shore. Thunder was expected to continue "on and off" into Wednesday.
The weather conditions in Canterbury and the upper North Island were linked, although the onshore flows were from slightly different systems, Murray said.
"The rain in Canterbury has the extra moisture because of the onshore flow. Likewise in Auckland the wind is sort of northwest, bringing in warm moist air at the surface.
"Although they're getting winds from different directions, aloft we have this big cold air pool that's giving instability ... that big cold air pool above New Zealand is giving the kick."
IS SNOW RARE IN NOVEMBER?
MetService meteorologist Claire Flynn said since 1990, heavy snow warnings had been issued five times during November, so while it was not common, it did happen about once every six years.
This week's snow, wind and rain were caused by a combination of a high to the south of the South Island and the slow moving low to the west, she said.
"With that high sitting to the south, it's just making southeast winds onshore in Otago and Canterbury, keeping the wet weather coming in, and snow at those higher altitudes."
The high was also keeping the low from moving away to the east as quickly as usual, Flynn said.
"With that high to the south as well, the wind is squeezing between that high and the low, making the wind quite strong around southern parts of the South Island."