Southerly winds are set to bring cooler temperatures to much of New Zealand on Friday and into the weekend.

It would be a big shock after summery highs were reached Thursday - Blenheim hit 29.5C and Ashburton 27C.

In Tauranga, temperatures are expected to reach around 21 degress today before dropping down to 10 overnight.

MetService meteorologist John Law told Morning Report the cooler weather will make its way up from Marlborough into Wellington and along the East Coast of the North Island throughout Friday.

"A real dramatic change yesterday, about 20C drop from Christchurch high yesterday to what we've got at the moment, around about 6C there (this morning).

"I think that difference is going to be much more noticeable after that warm day yesterday."

He says a change of wind direction means cold air from the Southern Ocean is being pushed across the country.

John warns the cold wet weather is expected to stick around throughout the weekend.

MetService has issued a heavy rain watch for Hawke's Bay north of Napier and Tai Rāwhiti from Friday afternoon until Sunday.

"So it's worth keeping an eye on there."

In Tauranga, showers are expected to develop in the afternoon. Heavy falls with thunderstorms and hail is also possible, says the MetService on its website.

Wellington, eastern Marlborough Sounds and Kaikōura coast have a strong wind watch for Friday afternoon and evening.

"Those southerlies set to pick up as we head through this afternoon as well and perhaps some stronger gusts there, perhaps even around about 90km/h, but that's going to add to those temperatures making it feel a fair bit cooler as well."

It follows a particularly wet and windy October and comes ahead of drought and fire fears this summer.

John says spring is always a volatile time of the year and while the changing winds aren't a classic El Niño pattern, he expects that weather cycle to take over as summer nears.

Meanwhile, the Avalanche Advisory is warning of a moderate avalanche risk for alpine areas at Mount Aspiring, rising to high alpine terrain for Aoraki Mount Cook and Arthur's Pass.

It says the strong winds and rain means lower freezing levels which could reduce the risk but that depends on the snow on Friday.

-RNZ.