Your Sunday may start off looking like a glorious summer day - but don't bet on it staying that way.

While most Kiwis basked in the sunshine yesterday, today is going to develop into a much more dreary day.

In Auckland cloud is set to increase with showers in the afternoon and evening - possibly heavy and thundery.

Northwesterlies will be developing as the morning progresses.

The inclement conditions could put a dampener on spectators gathering along Auckland's harbour to watch the America's Cup sailing field battle in the Prada Cup.

And there'll be more rain for the city as the week goes on, with MetService saying Aucklanders should expect heavier showers to hit midweek, from Tuesday to Thursday.

"Sunday marks the change to a more active weather regime for NZ," a MetService spokesman said.

"The unsettled conditions look to last beyond midweek but current information point toward a more relaxed situation by the weekend."

And it's not just the City of Sails with a grey and depressing weather outlook.

Northland and the Coromandel can expect cloud increasing today with showers developing during the afternoon and evening.

Thunderstorms are also possible.

Increasing cloud will also hit Gisborne with light rain developing late in the day.

MetService say that from Waikato to Wellington, including Bay of Plenty and the central high country there will be cloud increasing during the morning and periods of rain from afternoon, with heavy falls and possible thunderstorms especially in the west.

The same goes for Hawke's Bay, Wairarapa, Marlborough and Nelson.

Further down the Mainland, Cantabrians are in for a rain and thunderstorms in high country areas and brief falls elsewhere.

For Buller, Westland and Fiordland, Otago and Southland - similar periods of rain or showers, sometimes heavy, with squally thunderstorms and hail.

And in the Chatham Islands there will be "occasional drizzle".