Your weather: Rain to settle in across the country

Most of the North Island enjoyed fair weather on New Year's Day but it was a different story for the South Island, and the rain is set to spread.

MetService forecaster Aidan Pyselman said the first day of 2021 brought clear skies for much of the North Island, with hotspots reaching 28C in Masterton and Blenheim.

But it was "not so flash down south" with rain and thunderstorms overhead in inland Canterbury about the hills and ranges.

It is forecast that thunderstorms in the area from about Oxford southwards to the Saint Bathans Range and Kakanui Mountains may become severe and deliver localised downpours with rainfall rates of 25 to 40mm/h.

Severe Thunderstorm Warning issued for Canterbury Radar Area https://t.co/YhjcDUc7Kk pic.twitter.com/FKLqFXboru

— MetService Severe Weather Info (@MetServiceWARN) January 1, 2021

This may produce localised flooding. Hail is also possible.

A heavy rain warning is also in place for North Otago, Dunedin and Clutha from Balclutha northwards, from today until 11pm tomorrow.

Tomorrow, showers - some heavy - will become more prevalent throughout the country with some thunderstorms and possible downpours.

"It will be quite an active day tomorrow," Pyselman said.

Areas affected by rain will include central North Island, Coromandel, Waikato and the same places in the South Island.

"It is all happening," he said.

Party revellers out in Gisborne might escape the bad weather if they are lucky, he said.

"They may dodge it and then the very very top of the North Island [as well].

"Western coastal areas might also get away with not seeing the thunderstorm activity."

The North Island is still forecast to experience some shower on Sunday that will be possibly heavy and thundery in the afternoon in the north and east, clearing to fine in the southwest in the evening.

In the South Island rain is forecast on Sunday in the south and west and about the Canterbury High Country, easing in the evening.

Showers are still expected across the country into Monday with some fine spells expected in the North Island on Tuesday.