Auckland roads that have been worst-hit by flooding could take days to clear, the council says.

Photo: RNZ / Brad White

Torrential rain pelted the upper North Island overnight, causing flooding, slips, power cuts and forcing the evacuation of campgrounds.

Flooding was widespread from South Auckland to the Coromandel. In the Auckland region, civil defence dealt with flooding and scores of slips in the Hunua Ranges, Kawakawa Bay and Clevedon.

MetService has lifted its severe thunderstorm watch. While the worst of the weather appeared to be over for today, more heavy rain could be on the way on Friday.

Share your pictures of the flooding with us by emailing: iwitness@radionz.co.nz

Auckland Civil Defence said it had been "a busy 12 hours".

Photo: Twitter / Auckland Council

Photo: RNZ / Sarah Robson

In the city's south-east, flooding, slips and fallen trees had affected roads in Kawakawa Bay, Clevedon, Papakura, Beachlands and Maraetai. Several remained closed.

Auckland Transport would clear the roads as quickly as possible, but some might be affected for days, the council said.

Parks closed

Hundreds of campers, most of them children, were evacuated from regional parks.

The council has closed Tapapakanga, Hunua Ranges, Waitawa Regional Park, Duder and Waharau regional parks because of flooding and slips.

Park campers were relocated to higher ground. Engineers would assess tracks, bridges and slips once the weather subsided.

Photo: Supplied / Auckland Council

Camping groups rescued

The Fire Service have helped evacuate another school camping group from rain-struck south Auckland.

Senior station officer Chris Delfos said the group of about 180 adults and children from Hunua Falls Camp were rescued from a church hall on Falls Road in Hunua.

The children were at a community centre at Hunua School awaiting collection. Access to the camp was blocked by a fallen tree and flooding on the road, which emergency services and the military cleared.

Photo: RNZ / Brad White

That came after about 200 adults and young people from Stanley Bay School and Mangatawhiri School were evacuated from Camp Adair in the Hunua Ranges, where 160mm of rain fell overnight. The group was taken from the flooded YMCA camp to Hunua School. The children were either back at school or at home.

Fire Service senior station officer Chris Delfos said the children seemed to think it was all part of the school trip experience.

At Tapapakanga Regional Park campground, 30 campers were evacuated to Orere Point, where they would stay until roads reopened.

Auckland homes flooded, power out, roads closed

About 20 house flooding incidents were reported to Auckland Council.

Photo: RNZ / Brad White

Its call centre took 150 calls to anything from blocked drains and manholes to rising water levels. It received 50 reports of road flooding in the south and central area.

Nearly 2000 Auckland homes remained without power at midday. The biggest cut was in Papakura, where about 1600 homes were off line.

Lines company Vector said most damage was caused from trees on power lines or slippages pushing power poles. They were restoring power in some places as it went out in others.

In Kawakawa Bay, 15 houses were affected by flooding. Slips on Turei Hill stopped people getting out.

Photo: RNZ / Brad White

Slips around Beachlands made some roads impassable. Some motorists tried to drive through floodwaters and two vehicles had to be rescued, Civil Defence said.

One house in Maraetai was significantly affected by flooding. Flooding and multiple slips were reported on Waiheke Island.

Six Auckland schools and early education centres were closed, including on Waiheke Island. Scores were closed in the Coromandel/Thames area. See the list here

Cops, tourists flee

Two Canadian tourists camping near the Hunua Falls south of Auckland made an early-morning dash to rescue their gear - and themselves - from rising floodwaters.

Photo: RNZ / Sarah Robson

Robin Terry and Anisa Salmi had been travelling around New Zealand for about a month.

They were camping in the Hunua Ranges as the rain intensified overnight and the river near them suddenly rose.

They scrambled to get their gear together and made a break for it about 4am.

In the early hours, a police car was washed away while officers responded to storm-related jobs in Auckland.

They were returning from Kawakawa Bay about 1.30am when their vehicle hit sudden flooding on Clevedon-Kawakawa Bay Road.

The vehidle rapidly filled with water. The officers abandoned it, sought higher ground and were rescued by the local Fire Service.