Forecasters are on high alert with much of the North Island under weather warnings and watches and a tropical cyclone sitting in the Pacific which could intensify in the coming days.
A severe thunderstorm warning has been issued for Kaipara, Whangarei and Rodney, which is expected to bring torrential rain.
"These severe thunderstorms are moving towards the northeast, and are expected to lie near Maungaturoto, Kaiwaka, Brynderwyn, Warkworth, Wellsford, Kaipara Flats, Te Arai, Puhoi and Ahuroa at 4:22pm and near Maungaturoto, Kaiwaka, Mangawhai, Brynderwyn, Waipu Cove, Warkworth, Wellsford, Kaipara Flats, Matakana and Te Arai at 4:52pm," MetService said.
A severe thunderstorm watch has also been issued across 12 regions until Monday 9pm - Northland, Auckland, Waikato, Waitomo, Taumarunui, Bay of Plenty, Rotorua, Taupō, Hawke's Bay, Taihape, Wanganui and Manawatu.
MetService meteorologist Karl Loots told Newshub the severe thunderstorms could bring "torrential downpours".
"These storms are likely to bring localised heavy rainfall and possibly hail as well. In addition to this, there's a possibility that these can be quite slow-moving. So we can see localised downpours with these anywhere from 25 to 40 millimetres per hour."
MetService has also issued Coromandel Penisula with a heavy rain watch from Monday 7am to Monday 7pm.
And the already drenched Gisborne is in for some more rain. The region is under an orange heavy rain warning from Monday 7am to Tuesday 4am.
The front causing the weather is expected to weaken and move away from the country on Tuesday morning, taking the thunderstorms and rain with it.
"After this, we expect some welcome dry weather for the remainder of the week for the North Island," Loots said in a statement.
Cyclone watch
Tropical Cyclone Judy has just been named by the Fiji meteorological service on Monday afternoon. It currently sits north of Vanuatu as a category 1 system.
"There is increasing confidence that Judy will track well to the northeast of New Zealand with minimal impact on the country's weather," MetService said in a statement.
The cyclone is expected to be in Aotearoa's area of responsibility by Thursday.
"Large waves, heavy rain, and gale to storm force winds are expected to impact Vanuatu from Tuesday," MetService's bulletin said.
The tropical cyclone is then expected to reach severe tropical cyclone category 3 or above.
"It then turns southeast during Thursday and is expected to move out of the tropics later Friday."
Loots doesn't expect much impact from the low, but reiterated that the system has not yet formed fully and it's "extremely early days"
"These tropical systems can be very difficult to track, very far out, particularly before they have formed properly."
The low is expected to be within Aotearoa's area of responsibility by Thursday night.
In a tweet, NIWA shared the latest modelling from European Centre for Medium-Range Weather Forecasts (ECMWF) has many scenarios seeing the system move north and east of Aotearoa.
"Let's hope it stays that way."
MetService says another tropical low over the Coral Sea is likely to move east, with a chance of it developing into a tropical cyclone becoming low on Wednesday, moderate on Thursday and high on Friday.
"This system is expected to follow a similar track to tropical low 08F [the low mentioned above], and move across or close to Vanuatu later in the week."
