The warm weather is predicted to continue for the rest of the week as a ridge of high pressure sits over the country.
The first weekend of summer was marked by scorching temperatures nationwide, and Monday is expected to be even hotter.
Hanmer Springs was the hottest place in the country on Sunday at 31 degrees Celsius, according to MetService.
It's not just air temperatures that have been hot. According to NIWA's Ben Noll, ocean temperatures around New Zealand have been on average 2C warmer than usual - and up to 6C warmer off the West Coast. Water around the country has been warmer than average for more than a month now.
MetService Meteorologist Ciaran Doolin said: "It's good news for the working week. The (high pressure ridge across the country) is set to persist until Friday, which means a continuation of warm, settled weather."