Whanganui, Wellington, Taupo, Rotorua would all reach mid to high 20Cs this weeek with Taumaranui expected to be the hottest place in the country reaching 30C, Kandula said.
Northland's dry run would continue with a high of 28C, Auckland 27C, Hamilton 29C and Tauranga also 30C.
The South Island faces a wetter week hitting Fiordland and gradually moving up the rest of the west coast of the South Island tomorrow.
There was a short reprieve from rain on Tuesday before another front hit the west of the South Island on Wednesday and Thursday. The east of the South Island would be mainly fine.
Christchurch would dip to 26C midweek, Dunedin 22C, Blenheim 32C and Nelson 27C.
Kandula said the firefighters battling the raging Nelson fires would face similar conditions with moderate northerlies and seabreeze conditions continuing through to tomorrow.