Weather: New Zealand in for hot week, 30C possible on Tuesday

New Zealand is in for a hot and fine spell next week with some inland parts reaching around 30C.

MetService says Sunday marks the first in a string of days with a ridge of high pressure over the country.

"The high moves onto Aotearoa from the Tasman Sea, kicks off its shoes and makes itself comfortable into the middle of the week," it says on Facebook.

"For the most part... the next few days bring something resembling summer for much of Aotearoa."

WeatherWatch says this will push temperatures in inland regions of both main islands to around 30C on Tuesday, with the inland South Island forecast for daytime highs over 8C above average.

"Central Otago, inland Canterbury, and inland Waikato may all have some communities reach the 30C mark on Tuesday afternoon. Highs in the mid-to-late 20s are confidently forecast for most, although those in the coastal fringes of those regions won't be as mild," it says.

"The hottest main centre looks to possibly be Alexandra where a high of 32C is possible in the shade.

"Surrounding regions inland like northern Southland, Marlborough, inland Nelson and parts of Wairarapa and Northland will be in the mid-to-late 20s."

The coolest areas will be in coastal areas across New Zealand.

"Parts of Auckland [will be] exposed to the fading southerly flow off the Tasman Sea," WeatherWatch says.

"Sea breezes will have a cooling impact with easterlies on the beaches of Dunedin and Christchurch shaving 10C off the daytime highs, putting them around the 20C mark for daytime highs."