Temperatures in the mid-30s around the South Island yesterday have health officials warning extreme heat can be deadly.
Christchurch reached 36.1 degrees yesterday, breaking the city's record for the hottest December day.
Canterbury's Medical Officer of Health, Alistair Humphrey, said several consecutive days with extreme temperatures could pose health risks to people and animals.
Dr Humphrey said people needed to remember to be sun smart, drink plenty of water and stay out of direct heat whenever possible.
He said heat-related illnesses such as heat stroke could cause people to become confused, delirious and often unconscious.