Weather: New Zealand's hottest areas hit 37degC

Temperatures in the hottest part of New Zealand have soared to 37degC as the heatwave kicks in - and it's going to get worse.

"The temperatures are set to climb this afternoon with plenty of ka pai (great) weather around the country!" MetService says.

"With all this heat in the strong summer sun, remember to slip, slop, slap and be sun smart!"

Weather Watch says it's 37degC in parts of Napier and Hastings in Hawke's Bay, driving Kiwis to find cool water wherever they can. Witnessed report packed beaches, while Hasting's Splash Planet has been swamped by long queues.

Even the South Island isn't safe. Parts of the upper South Island are now 34-37degC, with the Marlborough Sounds on a sweltering 36degC.

And NIWA says a new all-time temperature record has been set in Richmond.

"The minimum temperature in Richmond only reached 24.3degC this morning!" it tweeted.

"That is a new ALL-TIME warm minimum temperature record for the Wider Nelson region. Records began there 157 years ago! The previous record was 23.7degC."

Tonight won't be much better, and Tuesday will see the heat return.

"A hot day in store once again for Tuesday, mostly sunny for the North Island but there may be some morning cloud in the west," Weather Watch says.

"Afternoon temperatures may get near the mid-thirties for parts of Waikato through to inland Taranaki."