MetService meteorologist Mmathapelo Makgabutlane said there was still "quite a lot of rain" forecast for the area, and it would be prolonged and persistent in nature.
Civil Defence controller Rob West said the slow-moving and prolonged heavy rainfall was forecast to continue until late today and had prompted the area’s first "red" heavy rain warning from the MetService yesterday morning.
The red warning remains in place this morning. In the 25 hours from 8pm yesterday through to 9pm today, up to 100mm of rain is expected to fall, on top of what has already fallen.
"This weather system is also coming in from the east, which we know from past experience can cause flooding in parts of Dunedin when the weather system stalls and heavy rain continues in one location," Mr West said.
"It’s important that everyone keeps up to date with the latest information as the situation develops into this evening, including via the Dunedin City Council website and social media channels."
MetService said the red warning meant "major impacts", including threats to life from dangerous river conditions, were possible.
Sandbags were available in St Kilda’s Ice Stadium carpark, Mosgiel’s Memorial Park gym carpark, and at the Middlemarch Showgrounds.
High demand for sandbags caused some traffic congestion in parts of South Dunedin and there were calls for residents to be patient.
The prolonged rainfall caused some surface flooding on roads around the city and coastal Otago, and there was a risk of more, as well as slips in some locations, as the weather event continued.
Otago Polytechnic will be closed today because of the rain.
While the DCC’s stormwater pumps across the city were functioning well yesterday, Mr West said contractors and
staff would monitor the network and were ready to respond to any issues throughout last night.
Otago Regional Council science and resilience general manager Tom Dyer said staff would keep a close eye on river and stream levels overnight, and flood response crews and extra contractors were on standby as a precaution.
Key rivers focused on included the Taieri River, the Silverstream, Leith Stream, the Pomahaka and Tokomairaro Rivers.
A message from the Mosgiel-Taieri Community Board said significant surface flooding was expected to occur across Mosgiel and the Taieri, and roads including Riccarton Rd, State Highway 87 between Mosgiel and Outram, and the Outram-Allanton highway could become impassable.
Clutha District Mayor Bryan Cadogan said the Clutha River was expected to flow as high as 2000 cumecs overnight, which was easily enough to "inundate" the Balclutha Aerodrome.
The council also closed some roads around the Milton area because of flooding yesterday.
All other catchments in the district were also affected, and the council has partially activated the Civil Defence plan.
Environment Southland general manager Lucy Hicks said further surface flooding across Southland was also expected today as heavy rain continued to fall across already saturated catchments, and river levels were high.
NZ Transport Agency Waka Kotahi (NZTA) journey manager Tresca Forrester urged drivers to plan ahead and check the latest road conditions today, because roads could close at any time — particularly in Otago where driving and road conditions were expected to be challenging through until this evening.
"The best thing people can do is plan ahead and avoid unnecessary travel which is now the advice from Emergency Management Otago."
Police also urged drivers to obey road closure signs after multiple vehicles were seen being driven around such signs in an attempt to continue their journey.
Dunedin police also made extra staff available overnight to assist with any emergencies relating to the weather.
People are urged to have a household plan, emergency supplies and getaway kits prepared, and advised to keep away from low-lying flood-prone areas, not to drive through any floodwater, act quickly to self-evacuate if you see rising water and be ready for power and communications outages.
The DCC did not anticipate the need to open a welfare centre in the city last night, but Mr West asked residents in low-lying parts of the city, including South Dunedin, to monitor regular weather updates as the weather event continued to unfold.
"We ask everyone to be patient, look out for each other and keep a close eye on reliable sources of information as this event continues."
