A state of emergency has been declared in the city of Detroit, Michigan and surrounding county as heavy rain caused flooding across the area. Video / AP

Jacinda Ardern has spent the day in Canterbury, which was devastated by torrential rain.

Heavy rain caused a deluge that flooded the remote Tairāwhiti settlement on the weekend.

There's flooding in the North Island today and snow expected down south overnight.

Hororata plasterer was stuck up a tree with raging floodwaters beneath him.

Chopper pilot saved stranded elderly woman unable to get across the Ashburton Bridge.

Dave Stewart and his family may have emerged from the floodwaters safe and well.

The Mid-Canterbury Farmy Army help clean up flood damage across the rural region.

Temuka local residents are pitching in to help out with the clean-up of the property.

'You're almost reduced to tears,' says farmer calling for more Govt help.

We can't call it a 'one-in-100 year' event, but can say climate change likely contributed.

"A big clean up job lies ahead of us," PM Jacinda Ardern says.

KiwiRail boss says repairs will take days.

Water levels slowly easing as hundreds of people plan to return to evacuated homes.

The Government has declared the flooding as an "adverse event" for Canterbury meaning $500,000 in funding can be unlocked for farmers and growers. Video / Pool

South Island shoppers will see gaps on the shelves today.

Mop-ups under way already but torrential rain continues to fall.

People in parts of Canterbury are being ordered to head to higher ground.

Climate change is why the Canterbury flooding earlier this year was so severe, researchers say. Video / George Heard / Hamish Clark / Supplied

The only way north out of Ashburton is by air - 17 roads shut, four bridges damaged and not passable, Ashburton District Mayor Neil Brown says.

Hundreds of residents have been evacuated and more wait for instruction as rivers rage in Canterbury. Video / Supplied / Hamish Clark / MetService

Dozens of schools are closed and residents are on standby as heavy rain continues to fall.

Ashburton is preparing for mass evacuations as the river rises and heavy rain continues.

Civil Defence is going door-to-door requesting Selwyn Hut residents to "evacuate now".

Heathcote River in Chch has broken its banks and next high tide will bring new flooding.

Floodwaters in Canterbury have exceeded warnings "by a huge magnitude", Fed Farmers says.

The Horowhenua District Council is pleading with residents to stop using water as the rain continues to be relentless in the lower North Island. Video / Paul Williams

The cost to Masterton homeowners could exceed $40 million in the event of a flood.