Slips and flooding have forced the closure of multiple sections of State Highway 2 in the Bay of Plenty and Gisborne areas, and the storm has caused damage in Dunedin.

The highway between Taneatua and Waimana is closed due to a slip, and heavy rain has caused flooding, completely closing the road between Opotiki and Gisborne.

NZTA said there was no suitable detour available, and motorists should consider delaying any journeys.

A third stretch of the road between Nukuhou and Kutarere is also closed - as well as its detour route.

The weather is wreaking havoc around the country, with flooding in Otago and Canterbury, too.

SH83 between Aviemore and Otematata in Canterbury will be closed until Sunday, January 10 because of flooding.

"A detour route is available and is suitable for all vehicles," an NZTA spokesperson said.

"Please take extra care on all roads and plan ahead if you intend to travel on the network today."

The latest update from the Dunedin City Council revealed the extent of the weather carnage.

"The heavy rain has caused some damage around the city and region however the stormwater and transport networks have performed well given the level of rain we experienced," a post on the organisation's Facebook page said.

"Our contractors are out and about cleaning up however there is still a risk of more rain and thunderstorms later today.

"We will continue to monitor the situation but there have been some minor slips and fallen trees so take care on the roads.

"Please avoid travel around Henley as contractors are cleaning up debris."

Sandbags are available now at the Dunedin Ice Stadium and the Mosgiel Memorial Park carparks.

A water tanker and further sandbags will be available for Middlemarch residents at the Strath Taieri Community Hall this afternoon.

Sandbags will also be available there.

A campervan crosses the Silverstream ford after leaving the Whare Flat Folk Festival at the Waiora Scout Camp, North Taieri, on Saturday. Photo / Otago Daily Times

Residents in Middlemarch are advised that they can resume flushing their toilets - but water may be contaminated.

"The heavy rain continuing through the night may have caused the wastewater system to be overwhelmed in places and there may be overflows onto roads," the Dunedin City Council said earlier today.

"People should stay out of any floodwaters and treat them as contaminated."

Before 9am, a second warning was issued for drivers to proceed with caution on Otago roads.

"Holidaymakers planning to return home, or resume their vacation and travel further in Otago today, are advised to check road conditions before they set out," Emergency Management Otago group controller Matt Alley said.

"Three state highways remain closed in the region as of 8am, with numerous local roads also affected by surface flooding, slips, washouts and debris.

"As well as roading issues, some councils had also issued boil water notices for communities whose water supplies had been affected by the flooding," he said.

"As people look to resume their travels this morning, we recommend they check the roading conditions before they leave, respect all road-closure signs and detours, and allow extra time to navigate their way to their destination."

Roads closed around Bay of Plenty.

Festival-goers stranded

Two hundred people are stranded after the rising water of Silverstream cut off the Whare Flat Folk Festival, northwest of Dunedin yesterday.

Festival organiser Kathryn Olcott said that the ford in Silverstream Valley Rd is closed and festival-goers at the site would be unable to leave until this morning.

She could not say exactly how many people remained at the festival.

Some festival-goers managed to get out before the ford was closed shortly after mid-day today.

The festival's final night of performances would go ahead today, she said.

Don't flush toilets

Overnight residents in Middlemarch were advised not to flush their toilets and avoid drinking water from bores as it was likely to be contaminated.

The Dunedin City Council advised earlier this morning that residents and visitors to the area should take care.

"With the inclement weather the wastewater system has been overwhelmed and we would ask that you refrain from flushing your toilet until further notice," a notice said.

"Extensive flooding and wastewater surcharges have affected Middlemarch and residents are being advised not to drink water from bores unless they treat the water with a filter or similar as it is likely to be contaminated."

Water will be available from a tanker beside the Strath-Taieri Community Centre from approximately midday today and people were advised to bring clean containers to fill.

"Sandbags will also be available at this location," said a council spokesperson.

"The overflows are contained on roads, but people should stay out of floodwaters in these areas and treat them as contaminated."

People in the southern area were also being told to "avoid travel on the roads unless absolutely necessary."

It's a wet and miserable day in Central Otago with flooding taking over Ranfurly Holiday Park. Photo / Supplied

Elsewhere, hundreds of people were also left stranded at the Whare Flat Folk Festival, northwest of Dunedin, after flooding closed the road in.

And campers in parts of the lower South Island were warned to move to higher ground, while those in Otago planning to start the commute home were urged to delay their travel until today.

Weather forecasts for around NZ

Parts of the North Island that were lashed by thunderstorms, heavy rain and more than a 1000 lightning strikes yesterday are bracing for more bad weather.

Yesterday MetService dished out heavy rain warnings and severe thunderstorm warnings to large parts of the North Island, while it detected 1100 lightning strikes across the North Island in just two hours.

The deluge flooded holiday hotspot Whangamatā with water, which covered Ocean Rd and lapped at the front gates of homes.

Severe weather warnings were also issued for Gisborne and Hawke's Bay yesterday.

An Aucklander on holiday in Whangamatā said there was a "massive downpour" that lasted 10 minutes, with thunder and lightning.

Whangamatā is in for showers today that could turn thundery from the afternoon, with a high of 24C.

Meanwhile, bursts of torrential rain pounded Auckland yesterday and the city is set to see more rain today.

Showers will develop late morning, and possibly turn heavier and thundery in the afternoon and evening. Light winds and a high of 24C is forecast for the city.

Parts of the east coast of the North Island that were forecast for heavy rain yesterday are in for more rain today.

This morning MetService said it also been a wet night in eastern Bay of Plenty with heavy showers and thunderstorms - and Whakatane has already racked up more than 40mm since midnight with still more on the way

In Horowhenua to Wellington there will be cloudy periods with a few showers some heavy about the Kapiti Coast until evening.

Marlborough and Nelson can expect cloudy periods with isolated showers about the ranges and there will be rain with heavy falls and thunderstorms possible, easing to showers this evening in Buller and Westland.

In Canterbury - the rain continues.

"A few showers, with thunderstorms possible, mainly this afternoon and evening," said a MetService spokesperson.

"Downpours and hail possible south of Timaru from this afternoon."

Otago, Southland and Fiordland will continue to be wet and wild with periods of rain, heavy at times along with thunderstorms, downpours and possible hail possible.