Record temperatures are being set around the lower South Island today, with Dunedin meeting a 1990 record of 32.7degC.
Scorching temperatures and gusty winds have seen temperatures up to 35degC and put firefighters on full alert.
A total fire ban across Marlborough has taken effect since 8am this morning.
The heat will be putting extra strain on the already stretched fire service which has dealt with two large forest fires in Marlborough in the past few weeks.
Principal rural fire officer Richard McNamara says there's an extremely high risk of a massive bush fire and people need to be sensible.
Oamaru has met the 1997 record of 31.7degC, according to MetService.
Christchurch temperatures are sitting at late-20's, mid-30's too.
Temperatures in the North Island are expected to be in the 20s.
Rain and lower temperatures are forecast tomorrow, but conditions are expected to improve for Christmas Day with mainly fine weather across most of the country.