Due to a large, complex low-pressure system over the Tasman Sea, rain and thunderstorms affected large parts of New Zealand on Friday and are expected to continue over the weekend.

MetService meteorologist Jessie Owen said, “This low is dragging warm, muggy air from the north down over the country, which combined with the extra heating we are getting from the sun now that we are heading into summer makes conditions ripe for showers and thunderstorms.

“A warm, muggy northerly flow is going to keep producing showers across most of Aotearoa through Saturday and Sunday, with the most shower activity expected in the afternoons and early evenings when the heating from the sun is at a maximum,” Owens said.

For the north and central parts of the North Island, there is a moderate risk of thunderstorms during the afternoon, evening, and night.

These thunderstorms may produce localised heavy rain with intensities of 10-25mm per hour and there is a low risk of them becoming severe with downpours of 25-40mm per hour.

For Whanganui, Manawatū, Horowhenua, Wairarapa and parts of Hawke’s Bay, Kapiti and Wellington, as well as Buller and inland areas of Tasman and Marlborough, there is a moderate risk of thunderstorms during the afternoon and evening, bringing localised heavy rain with intensities of 10-25mm per hour.

MetService has issued heavy rain watches for central and eastern areas of the South Island for the next 24 hours.

Rainfall amounts were forecast to approach warning-criteria level overnight on the Kaikoura coast and ranges, with periods of heavy rain and possible thunderstorms likely to begin at 10pm and ease around 9am today.

Periods of heavy rain were also expected in Canterbury, North Otago and Dunedin overnight Friday and forecast to continue throughout Saturday.

MetService is advising people to keep up to date with the latest forecasts in case any watches are upgraded to warnings, or more areas are added.