WeatherWatch has forecast some parts of the country are tipped to see temperatures soar to 30C on Tuesday.
It says Canterbury is most likely to reach 30C alongside Hawke's Bay and Northland.
Crabtree said it is not expected to be as warm further south.
"It will be pretty average temperature-wise. There will be just a few showers around and then relatively fine for these inland areas but it's definitely through Canterbury where the warm and very fine weather is going to be."
Temperatures are expected to reach 21C in Dunedin on Monday and 22C on Tuesday.
The extremely warm weather will be short-lived, Crabtree said.
"The warm temperatures are mainly during today and tomorrow. It's still relatively warm moving through to Wednesday but we do have a shift in the weather later on this week dropping back to more average temperatures and probably a little bit cooler especially for the southern areas."