Weather: Brace yourself for a wet and windy week

Brace yourself for a wet and windy week as a deep low pressure system moves over New Zealand, MetService warns.

Auckland and the upper North Island can expert a fine and cloudy start, but showers, possibly heavy this afternoon and evening is expected to hit Bay of Plenty, Waikato and Waitomo.

The humid conditions would also see temperatures soar into the high 20s in Invercargill with a forecast of 28C on Monday.

"A ridge over the country retreats slowly eastwards on Monday as a deep low pressure system over the Tasman Sea moves eastwards," MetService says.

"During Tuesday and Wednesday, the low is expected to move east over New Zealand, bringing rain and strong north to northwesterly winds over much of the country. It is followed by a ridge on Thursday."

Rainfall accumulations reaching "warning criteria" are forecasted for Westland on Tuesday through to Wednesday - and likely also for Buller, Nelson and western Marlborough.

MetService said there is also possibility of northwesterly winds becoming severe gale in exposed places of Wairarapa, Hawkes Bay and Gisborne on Wednesday.

"There is low confidence of severe north to northwesterly gales in exposed places of the west coast of the South Island including Nelson and Marlborough and north Canterbury, and in the north and west of the North Island from Northland to Bay of Plenty to Wellington during Tuesday and Wednesday," MetService said.

"But the confidence should increase to moderate for Wellington overnight Tuesday."

Today, it will be mostly fine except for a few showers about the ranges for Horowhenua Kapiti Coast and Wellington.

Mostly fine also for the rest of the North Island but a few showers mainly inland during the afternoon and evening, some heavy with thunderstorms.

Canterbury and Otago started the day with areas of fog and look likely to end with the same this evening.

Weather this week:

Monday: North Island, cloudy periods with a few showers possible during the afternoon. South Island, Mainly fine in the east, a few showers turning to rain south of the Glaciers and Northerly gales in Fiordland.

Tuesday: North Island, cloud increasing with a few showers and possible gale northeasterlies in some areas. Rain developing in Northland late in the day. South Island, heavy falls and cloud increasing in the east, and rain forecasted in the west. Northeasterlies rising to gale is being forecasted for the coasts.

Wednesday: Heavy falls north of Taranaki to East Cape, easing to a few showers. Strong or gale northeasterlies easing. Rain, possibly heavy in the north and west of the South Island, and showers developing in the south.