A warm but unsettled week around the country is being forecast for this week.

Northwest winds are expected bring a bout of potentially significant heavy rain to the West Coast of the South Island, says the MetService.

A slow front moved across the north-eastern parts of the country, which continued to feed rain into the Bay of Plenty and the northern ranges of Gisborne.

It was a very warm start to the week, with many spots of the North Island recording an exceptionally warm Sunday night.

Whakatāne, for example, reported a minimum temperature of just 16.8°C in the early hours of Monday morning.

The warm temperatures are set to stick around and reach into the twenties for much of the country by the middle of the week, with the highest temperatures set for locations in the east.

Napier could see daytime temperatures reaching 29°C on Wednesday.

A feed of air from the north and west is responsible for these warmer temperatures, but MetService is cautioning that along with the warmth, these winds will also be bringing some windier and wetter weather to parts of the country.

MetService has issued a Severe Weather Warning for heavy rain in Westland on Wednesday with rainfall totals more than 300mm possible about the ranges.

Severe Weather Watches have also been issued for rainfall in Fiordland and about the headwaters of Canterbury and Otago.

Additionally, winds could reach severe gale through exposed parts of the Canterbury High Country, Fiordland, Southland and the Queenstown Lakes District.

'With the winds arriving from the Tasman Sea wet weather will push onto the West Coast of the South Island on Tuesday before spreading onto the North Island for Thursday.” says MetService meteorologist John Law.

"While the wettest weather is set for the ranges of the West Coast, strong north-westerly winds will push some rain over into the east as well. Inland parts of Canterbury can expect some heavy rainfall driven across into the headwaters of the eastern rivers."

For the latest Tauranga forecast, visit the MetService website.