Motueka, Blenheim, Kaikōura and Christchurch are under heat alerts, with temperatures expected to hit or exceed 30 degrees.
All up, 14 towns and cities around New Zealand have heat alerts today as temperatures continue to climb.
"Records could roll," MetService said.
MetService meteorologist Mmathapelo Makgabutlane says two weather systems are moving across the South Island, with the first beginning early this morning.
"That will bring an increase in wind speed and summer rain for western parts of the country but as we head into Sunday we have a larger weather system that arrives and that also ramps up that rain in the western part of the South Island and strong winds for almost the whole of the South Island."
The norwesters will drive temperatures up and last overnight in both islands, with temperatures staying in the high teens."It will be much warmer than average for some parts of Northland and Coromandel," on what is shaping as "a classic summer weekend" for the North Island, she says.
There are several watches and warnings in place.
Orange heavy rain warnings are in place for Westland and Fiordland, where up to 300mm could fall over a 30-hour period from late tonight.
A heavy rain watch also applies to the ranges of the Grey and Buller districts from midday tomorrow while there's a strong wind watch for Marlborough, especially about the Sounds and Kaikōura Coast from 1am tomorrow.
An orange strong wind warning has been issued for Canterbury about the High Country and the foothills from 10pm today. Severe gales northwesterlies gusting up to 130 kilometres are predicted.
Heavy rain and strong wind watches are also in place for the headwaters of the Canterbury lakes and rivers in the Arthur's Pass area.
Heavy rain watches and strong wind watches have also been issued for the weekend for the headwaters of the Otago lakes and rivers, Fiordland, Otago, Southland and Stewart Island.
North Island also sweltering
Paihia and Russell, Whangārei, Whitianga, Tauranga, Whakatāne, Gisborne, Napier, Hastings, Masterton are also under heat alerts today.
Hastings is likely to be the hottest place with 35 degrees forecast and that's due to climb to 38 degrees on Sunday - 12.7 degrees above average.
Fire bans in place
Fire and Emergency warned the weekend's conditions - heat, wind and low humidity - were a "perfect storm" for wildfires.
The risk was highest in Canterbury, Marlborough, Wairarapa, Hawke's Bay, Tai Rāwhiti, and Northland, it said.
In several areas across the country fires are banned or restricted.
Fenz Southern district commander Craig Gold said galeforce northwesterly winds, high temperatures and low relative humidity added up to high fire danger.
Any rain which fell today was unlikely to reduce the risk significantly.
"It’s really not the time to be lighting fires of any kind," he said.
"That goes for farmers, contractors and forestry managers, but also for holiday-makers."
Most of inland Otago was in a restricted fire season, so permits are needed for outdoor fires. Permits include conditions which prevent fires being lit in windy conditions, or when strong winds are forecast.
This applies to recreational fires as well as land management fires.
"A camp fire by the river or a bonfire to celebrate the season can have devastating consequences if they escape, and will be very challenging for firefighters to put out in the high winds we’re expecting."
People often lit recreational fires with good intentions but did not realise the danger.
"Please find another way to celebrate summer.
"Our firefighters have got plenty to do already.
"If the party is at your place this holiday season, we actually prefer not to be invited, especially to an emergency."
Red zones have a total fire ban, and in yellow zones, people may need to apply for a permit - go to checkitsalright.nz to check and apply.
All permits in Canterbury are suspended from midnight Friday until 8am on Monday.
There's no permit needed in green zones.
- Additional reporting Allied Media
