Fire warning as NZ swelters under 35degC temperatures next week - NIWA

New Zealand will be at greater risk of having bush fires when Australia's hot weather makes its way over the ditch next week.

NIWA forecaster Chris Brandolino told The AM Show temperatures won't reach Australia's record breaking heat, but the hot weather is coming.

"We've talked about Adelaide, 46.6degC... Some of that is going to make its way over as early as Sunday this weekend."

Auckland won't be affected too much, but the interior of the North and South Island will be scorching hot, Mr Brandolino said.

"The fire danger is going to go up. It's going to be difficult sleeping if you don't have the fan or AC.

"This is going to be a prolonged, kind of accumulative event where maximum temperatures in the warmest locations either approach or exceed 35degC."

Firefighters in Canterbury are already preparing themselves for a busy fire season in light of the hot, dry forecast.

Strong vegetation growth has led to plenty of tinder-dry long grass across the South Island.

"It's very hot and dry now things are drying out," Station Officer Owen Patterson, who works in Lumsden, Southland, told Newshub at the start of January.

"We've had a lot of high winds here now [and we've] got to be very careful [as] things are getting very dry."