We're in for scorching hot weather for the next couple of weeks as a heatwave brings hot days and warm nights across the country.
Northerlies will boost temperatures even further - ranging in the low to mid-30s nationwide, WeatherWatch says.
While temperatures soar, St John recommends drinking plenty of water and keeping a vigilant eye on the vulnerable - children, infants and elderly.
A sub-tropical low is expected to drop south over the country next week, bringing with it heavy rain, strong winds, large seas and extreme humidity to some regions, WeatherWatch says.
The muggiest of conditions will be felt in northern part of the North Island, with temperatures above 30degC expected.
The Waikato is expected to experience 90 percent humidity, WeatherWatch head forecaster Philip Duncan says.
Aucklanders will get some relief next week with temperatures hovering in the late 20s.
And Central Otago will bear the brunt of the heatwave, with temperatures soaring to the mid-30s and highs of 30degC forecast for Southland on Monday.
The high temperatures around the country have been reflected with gardeners and growers saying that some fruits have ripened early and plants blooming early as well, Mr Duncan said.
Staying hydrated is crucial
St John Christchurch Metro Territory manager Craig Downing advised people have a minimum of two litres of water each on hand when travelling.
"People can lose a lot of fluids through sweating and heat. Maintain hydration throughout the day, rather than bulk drinking and then nothing for a long time.
"If you feel faint while driving, immediately pull over to where it is safe, call for help, put the car safely in park and turn fans on high to move fresh air around the car."
Be aware of young and old
Children, infants and elderly should be kept an eye on, Mr Downing said.
Infants need to be in a room with circulating air and parents should monitor children for dehydration.
Elderly people were at a risk of collapsing and heart conditions could increase in the heat due their frailty, he said.
They may also be less inclined to seek help, so people should check on their elderly neighbours, he said.
Fire and Emergency New Zealand southern shift manager Brent Dunn said "it's pretty dry".
He encouraged people to check with their local council to stay up to date with what fire restrictions are in each area.
"And if you see smoke ring 111."
At 3:45pm on Wednesday, Mr Dunn said South Island fire crews had responded to four fire callouts out of a total of 30 calls - made up of medical and motor vehicle accidents and false alarm calls.
Look after your pets
SPCA communications manager Jessie Gilchrist said people should take extra care if exercising their pets in the heat.
She said exercising in the scorching sun and during the hottest hours of the day could be dangerous, and recommended exercising pets early in the morning or late at night when it was cooler.
On warm days, the inside of the car can heat up "very quickly", even when cars are parked in the shade, she said.
"Please don't leave your dog unattended in a car at any time of the day. If the purpose of your trip is not to take your dog somewhere, please leave your dog at home," she said.
And just like humans, animals can get sunburn too.
People should also be aware that hot pavements can burn and blister their pads of their paws, she said.