Part of State Highway One is flooded after a burst of heavy rain across central Auckland for a short period this afternoon.
Flooding has now receded in the left-hand southbound lane at the Panama Road overbridge, between Mt Wellington and Ōtāhuhu.
However, NZTA advised motorists to take care on the southbound Takanini on-ramp where there has been flooding.
Metservice said there was heavy rain for a short period in central Auckland. Showers are forecast for the rest of the day.
A thunderstorm watch valid to 10pm today covers Taupo and south to Hawke's Bay, Taihape, Wanganui, Manawatu, Tararua, Kapiti-Horowhenua and Wairarapa.
The worst of the weather has passed for parts of the North Island, with Metservice lifting its heavy weather warnings.
But the remnants of heavy rain overnight are still being felt in parts of the country.
While heavy rain has eased in Auckland, Waikato, Gisborne south of Tolaga Bay, and Hawkes Bay from Hastings northwards, heavy rain is expected south of Hastings, Wairarapa and in parts of Marlborough.
The rain is also expected to push as far south as Christchurch.
Metservice says low pressure off the coast of Taranaki is shunting the wet weather towards the South Island, and says Cantabrians could be set for a wet Christmas.
But MetService says people in the Otago region should prepare for hot weather, with Wanaka and Queenstown the pick of the country, expecting 30 degree temperatures.
Meanwhile, Bay of Plenty, Coromandel Peninusla, Gisborne, Northland and Rotorua have all experienced heavy rain, causing surface flooding on several roads.
Drivers making their way down SH1 just before the Te Kauwhata exit are urged to take caution due to flooding. The New Zealand Transport Agency (NZTA) says due to a slip on State Highway 25 Coromandel to Te Rerenga heavy vehicles are not suitable and caution is advised.
There are also reports of a serious crash blocking SH1 in the central North Island.
The highway is blocked north of Foxton at the Paranui Road intersection, NZTA says.
Delays are likely.
And State Highway 54 near Hunterville is partially blocked by a fallen tree.
A temporary 30km/h speed limit is in place south of the intersection with SH1.
The weather has cleared up a little in Coromandel and Northland in recent hours but MetService says there is a chance of more rain and isolated thunderstorms for the rest of the day.
King tides and strong onshore winds could cause flooding along parts of the East Coast in the North Island later today.
The atmospheric river affecting the North Island is a striking feature on a hemispheric scale.— NIWA Weather (@NiwaWeather) December 24, 2018
Along a narrow corridor, moisture is stretching from Papua New Guinea to New Zealand! pic.twitter.com/94S1BBwiHD
Campers at several spots on the Coromandel Peninsula were moved to high ground yesterday as a precaution after flooding, with more than 100mm was recorded in less than 24 hours in parts.
Meanwhile at Waihi Beach, the sun is shining this morning following two days of heavy rain that caused flooding.
The South Island is the place to be today and Otago, Southland and Westland are set for a fine day with temperatures of 30 degrees in parts.
Meteorologist James Millward said it was looking like Wanaka would be the hottest spot in the country with 31 degrees predicted.
"Christmas Day itself is looking really nice and fine if you're down through Southland, Otago, Dunedin, Westland - you're going to have a really nice day and temperatures kind of approaching 30 degrees through there."
The outlook for New Year's Eve at the moment predicted some strong westerly flows and possibly showers in the west but the eastern areas looked good, Mr Downs said.