MetService is predicting warmer temperatures over the coming days, thanks to a hot nor'wester coming over from Australia.
Temperatures as high as 40°Celsius are expected throughout New South Wales over the weekend.
MetService said temperatures in New Zealand would not be as high as Australia, but some areas would be much warmer than usual for this time of year, particularly overnight.
Meterologist April Clarke said the nor'wester would move across the South Island tomorrow and the north on Monday.
Napier and Hastings would be up to 25°C on Monday, and the highest for the South Island would be Blenheim - up to 24ۜ°C tomorrow.
"Overnight temperatures are looking higher. So, for example, places like Oamaru and Alexandra are 13°C overnight, which is quite a lot warmer than what they've been having.
"It's warm air from the north and it will carry a bit of rain, but it's not a heat-wave which is defined as 5°C above average temperatures for five days."
The election weekend coincides with the spring equinox and the start of daylight saving, when clocks go forward an hour early Sunday morning.