The rain and blustery winds that are bringing an end to the settled spell of summertime weather have a chilly southerly sting in the tail.

A severe thunderstorm watch has been posted for Auckland this afternoon.

Valid until 11pm it warns of possible thunderstorms in Auckland, Waikato, Waitomo, Taumarunui,
Taupo and Taranaki.

Metservice says a front preceded by very warm moist unstable air is expected to move onto the west of the North Island later this afternoon.

"Embedded thunderstorms are likely in the band of heavy rain as it moves through," they say.

"This is an alert to the potential that one or two thunderstorms may become severe supporting possible rainfall rates of 20-40mm/hr, damaging wind gusts that may exceed 110km/hr, and the possibility of an isolated tornado, especially in coastal locations."

The MetService said in a tweet the southerly would bring much colder temperatures throughout the country, with snow in the Southern Alps tonight.

The southerly was passing through Dunedin around 2pm, and was due into Wellington about 10pm,  MetService media and communications meteorologist Daniel Corbett said.

Once the southerly arrived daytime maximums were expected to be in the high teens to low 20 degrees celsius.

"The southerly change will be something to be reckoned with," Corbett said, although by the time it got to Auckland the temperature drop would not be as dramatic as it was further south.

MetService also raised the possibility of strong northwesterly winds about Wellington and Wairarapa ahead of the southerly.

"It usually tends to peak just before the cold front of the southerly change comes through," Corbett said. By mid-afternoon winds were gusting up to 80kmh in Wellington.

Rain was falling throughout much of the country today, although Hawke's Bay and Gisborne were mostly expected to get their wet weather overnight or tomorrow.

More settled weather was expected to return in time for Waitangi Day on Wednesday.

"Much of the active weather will have moved through by Tuesday, bringing a mostly fine and settled Waitangi Day across New Zealand," Corbett said.

- © Fairfax NZ News