Waitangi and the Bay of Islands will enjoy a beautifully sunny day with light winds, while further south Auckland will receive warm and mostly sunny weather, Doolin said.
Hamilton will begin Waitangi Day will low cloud and fog before a warm and fine afternoon, while on the other side of the Kaimai ranges, Tauranga will have a stunning day with gentle sea breezes.
Christchurch will be sunny and hot, with a northwesterly bringing "nice, warm dry air", Doolin said.
Parts of Otago may be plagued by potentially heavy rainfall during the evening, which may arrive to areas south of Christchurch closer to midnight, he said.
Weather outlook for the main centres
Waitangi - 29C mostly sunny with light winds.
Auckland - 26C mostly sunny with light winds.
Hamilton - 28C morning low cloud/fog, then fine. Westerly breeze.
Tauranga - 27C mostly sunny. Northwest breeze.
Wellington - 20C mostly cloudy, drizzle towards evening. Strong northwesterly.
Christchurch - 31C sunny and hot. Strong northwesterly.
Dunedin - 26C fine, strong northwesterly. Evening rain and southerlies.