Campers in Waihi have been forced to flee after a campground in the southern Coromandel town flooded early on Monday morning.
Emergency services were called to Top 10 Holiday Park at Waihi just before 3am, when the grounds were inundated with water.
Michael Gatt, who has a permanent caravan at the campground, says he heard the rain falling all night and opened the door to find the area flooded.
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"There's two campgrounds on Waihi Beach and they're both flooded. Some of the streets and properties are flooded as well," he told Newshub.
"The rain eased off earlier and the water has resided quite a fair bit but we're expecting more tonight so we're in the process of packing up to go home [to Auckland] for a couple of days and then come back."
An image posted online shows Mr Gatt's trailer submerged in knee-deep muddy rainwater as campers nearby wade through it.
A Fire and Emergency spokesperson says campers were moved to the local RSA as a precaution.
"The amenities are underwater and the kitchen's underwater," said Mr Gatt, adding that campers "pretty much can't use anything" and have been forced to leave.
"We're okay - we're dry at the moment but we can't use the facilities so we're heading home."
He said he hasn't noticed any damage to his caravan, but will check on it again when he returns to the campground from Auckland on Boxing Day.
"We'll see what the rain brings tonight."
The wet weather is set to continue across the North Island into Christmas Day.
NIWA has called the weather pattern a "tropical firehose" of moisture flowing toward New Zealand, while Weather Watch says it's a "large low".
Over 100mm of rain was recorded at multiple gauges in the Coromandel overnight, according to MetService, as heavy rain loomed over the region.
MetService forecaster Andy Downs told Newshub the heavy rain could cause localised surface flooding and "maybe even more significant surface flooding" in some places.
King tides were forecast for Auckland's Tamaki Drive, Tauranga, and the Firth of Thames.
"Over 90mm of rain has fallen this morning in Tauranga - hourly rates up to 20mm an hour," Mr Downs said on Monday.
The heaviest rain is expected in Northland, Coromandel Peninsula, Bay of Plenty and Gisborne from Tolaga Bay northwards and a 'Heavy Rain Warning' is in force by MetService.
Christmas Day will bring "heavy rain" with "torrential falls possible then easing overnight" Weather Watch says.