Flooding is being reported in Tauranga and Rotorua as heavy rain pounds the Bay of Plenty, with MetService issuing fresh warnings this afternoon.
Police are warning motorists to take "extreme caution", saying there had been a number of calls for assistance to emergency services due to surface flooding and fallen trees.
Police said there could be hidden hazards in areas where there is surface flooding.
"If you can delay travel, we would advise you do so until the weather event has passed."
In Rotorua, firefighters helped take children off a school bus stopped due to flooding on Homedale St.
A motorist reported not being able to get home due to flooding on Hodgkins St at the intersection with Hamon Pl.
Police say State Highway 1 is closed just north of Tokoroa, following a serious crash involving two vehicles reported at 4.10pm. People have been injured
In Tauranga, two cars earlier crashed on the Maungatapu onramp to State Highway 29A.
A police spokeswoman said there was "significant surface flooding" in the area and asked motorists to drive to the conditions.
Surface flooding is also being reported in Mount Maunganui's Campbell Rd.
Holly Collins said she was visiting a friend on Campbell Rd and part of the road was closed off due to flooding.
"The water is up to our knees."
Collins, 21, said a man had been handing out sandbags for residents on the street to help stop the flooding.
The water was "ankle-deep" in her friend's garage.
Her van was also outside stuck "under-water". "We can't move it."
Another resident said water on her street was knee-deep and bins were floating down the road.
A person on the street was also working to push their vehicle which was stuck in water.
She said it appeared the road had been closed.
Rotorua Lakes Council urged people to travel only if necessary given the rain with trees down and surface flooding being reported in various parts of the Rotorua district.
"The number of weather-related calls to Rotorua Lakes Council and its contractors has increased in the past hour or so after a reasonably quiet morning."
Crews had worked to clear blocked cesspits and drains, clear downed trees and manage surface flooding.
Tauranga City Council also reported localised flooding.
This included Huia Ave/Carysfort St of Mount Maunganui.
"Our contractors are out doing what they can to sort things out and they're on their way to Huia Ave"
An orange warning for heavy rain is in place for Rotorua and Bay of Plenty through to midnight tonight. A severe thunderstorm watch is also in place until 9pm with hail possible and strong northeasterly winds.
MetService said 50mm of rain had fallen in Rotorua in the 12 hours since midnight, while 20mm had been recorded in Tauranga and 10mm in Whakatāne.
Elevated parts of the Coromandel Peninsula have had 100mm of rain since midnight while 70mm of rain had fallen in Waihi in five hours this morning.
MetService meteorologist Luis Fernandes this morning said things were set to get worse as the day went on.
"As you've probably noticed, the rain is starting to kick in in your area after a very wet night up north. The main band of rain, which was approaching from the northwest, would be significant to heavy.
"This would continue for most of the afternoon but would ease up a little in the evening.
The severe weather forecast team predicted between 80-110mm of rain today.
"This is significant."
But possible thunderstorms were also forecast, which Fernandes said could involve periods of heavy downpours as well.
He was not able to pinpoint any particular areas that might be impacted the most as the warning covered the entire region.
He advised people to take care and precautions whenever there was a period of heavy rain.
"There is always a likelihood you can have swollen rivers and things of that nature."
Drivers were advised to be cautious, as well as anyone needing to cross streams or rivers.
Localised flooding was also a possibility with the thunderstorms.
"It is a matter of people being a little more cautious and taking it easy on the roads, keeping their wits about them."
For the rest of the week, Fernandes said there would be showers in the morning on Tuesday and Wednesday, with rain expected on Thursday as well. There could be some heavy rain but there were no watches or warnings in the region yet.
"It's quite an active week, there is a lot going on with several systems moving across the country.
"The tap will be on and off, on and off."
A deepening subtropical low moving southwards over the Tasman Sea is driving the weather in combination with an associated front moving southeastwards across the country bringing strong winds and rain to many areas.
The orange warning is also in place for Coromandel and a heavy rain watch is in place for Taupō and Tongariro National Park until 5pm today.
Taupō can expect periods of rain, possibly heavy turning to showers this afternoon.
An Emergency Management Bay of Plenty spokesperson said there had been no reports of issues or damages by mid-afternoon, but there may have been small-scale incidents handled locally.
In terms of preparedness, they said strong winds can take out power, and even small scale flooding can make roads temporarily impassable.
"We always advise people to stay clear of flood water- even if it looks shallow.
"That's because you don't know what's underneath and even a low level of water has the potential to wash away a person or a car."
In case of power cuts you should always check you know where your torch and batteries are and keep your phone charged.
"Don't forget you can use your phone as a radio as long as it has power."
Meanwhile, hundreds of Bay of Plenty residents experienced power outages this morning.
Powerco reported affected residents were in Waihi and Pāpāmoa, and the outages were due to damaged equipment.
Power was estimated to be restored by 9.45am for Waihi and 11am for Pāpāmoa.
Three high-end businesses fear works could shut their doors forever.