Warning as heat rises to 26C and strong winds hit South Island

Winds gusting more than 100 kilometres an hour have been recorded on Stewart Island as gales and hot temperatures hit the South Island.

Fire and Emergency warned the heat, strong winds and dry conditions in parts of Canterbury would make it easier for fires to ignite and spread.

By 10am, Banks Peninsula recorded a temperature high of 26 degrees, the warmest in the country.

MetService said the mercury was expected to climb into the late 20s for parts of Canterbury, Blenheim and Dunedin with the eastern regions of the North Island also preparing for a scorcher.

But a cold change was expected to hit later on Thursday with temperatures dropping by 10 degrees in Dunedin in the evening.

MetService has issued a strong wind watch for northwest winds about Otago and Southland until 7pm, turning to southwesterly gales about Dunedin and coastal Clutha.

A strong wind watch for west to northwest winds possibly approaching severe gale had been issued for Wairarapa and Hawke's Bay south of about Hastings from midafternoon on Thursday.

A heavy rain watch was in place for Fiordland.

Fire and Emergency Canterbury community risk manager Dean Harker said the strong winds were a concern and people should reconsider mowing, welding or other work that might create sparks when it was dry and windy.

"Any fire or embers can be spread really quickly and get into some of the other drier vegetation that is around the area at the moment," Harker said.

"The vegetation is drying out. It may be green on the top but there still are dry fuels underneath."

He urged anyone intending to burn off in the coming days to go to the Checkitsalright website to ensure it was suitable.

People who might have burned in recent days or weeks should also make sure those burn piles were fully extinguished, he said.

"We've had a couple of episodes lately where the wind has got up and it has knocked the top off the burn pile and the hot embers are still underneath the ashes and the fire's reignited and got into some other vegetation in areas, which has caused other unnecessary fires."

Canterbury remained in an open fire season, but Harker said people should ring the Fire and Emergency communication centre to let they know about any burns off and leave a contact number.

He also encouraged people to have access to water to extinguish the fire and put a sign outside their property - which might be available to borrow from a local fire brigade - stating there was a controlled burn off.

Metservice's Canterbury weather radar upgrade

MetService's Canterbury weather radar was back in action following a $3.5 million nine-week replacement project.

The work involved demolishing the 30-year-old radar and concrete tower, and installing a stronger 19 metre-high steel tower and new radar on top.

MetService said the radar site south of Rakaia provided 300 kilometres of coverage, encompassing the entire Canterbury region, central Southern Alps and parts of Marlborough and Otago.

Chief executive Stephen Hunt said the radar used the latest dual polarisation technology to identify different types of precipitation - rain, hail or snow - and would provide more detailed weather information for the region.

"Our meteorologists will use this to enhance our weather forecasting and severe weather warning services for central South Island communities, and for aviation, and civil defence agencies," he said.

"We are aware that the Canterbury radar is well-loved by the region and are pleased to be able to deliver improved services through this leading-edge technology."

MetService said the radar could pick up the size of droplets and their density so forecasters could determine rainfall rates in real time.

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