Lightning strikes have been recorded in Northland and Auckland as storms roll across the top of the North Island.
MetService has issued a severe thunderstorm watch, covering Northland, Auckland, Coromandel Peninsula, Waikato, Waitomo, Taumarunui, Bay of Plenty, Rotorua, Taupo and Taihape from Monday afternoon.
"These thunderstorms may become severe bringing localised rainfall rates of 25 to 40 mm per hour," MetService said.
"Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips."
The rain is expected to set in from the afternoon, with the watch lasting until 10pm.
A strong winds warning was in place over Remutaka Hill, on State Highway 2.
SH2 northbound from Wellington has re-opened after it was partially blocked by downed power lines, which were brought down by bad weather combined with probable salt corrosion.
Traffic was backed up for several kilometres but had since eased, Waka Kotahi said.
Early on Monday afternoon, Wellington Electricity said a fault crew had secured the stray wires and another crew was on its way to fix them.
The storms seemed to affect small parts of the South Island too on Monday too.
Bay Plenty, including Rotorua, and Waikato, may potentially face heavy rain all the way through to Boxing Day.
