Temperatures have hit 30 degrees Celsius and above in northern parts of the country, with heat alerts in place for Auckland and Te Kuiti.
Whangaparāoa, north of Auckland, rose above 30C for a time this afternoon and has settled slightly back down to 29C. MetService said it was the area's hottest temperature this summer.
MetService said it could even rise further about 3-4pm - typically the hottest time of the day - but southwesterly winds are forecast to develop soon which would cool it down.
A heat alert is in place for Auckland, with Auckland airport reaching 28C and is currently hovering about 27C with southwesterly winds.
Further north, MetService's station at Marsden Point in Northland hit 32C. While Whakatāne was at 29.6C - the region's warmest temperature this summer - Tauranga at 28.8C and Hamilton at 28.8C.
However, cooler weather was set to settle in over the next few days, MetService said.
On Tuesday, Tauranga Airport was the hottest location, recording a maximum temperature of 30.4C.
Twizel hit 30.1C.
Springs Junction has the coldest minimum temperature, at 5.7C.
Canterbury will move to a prohibited fire season from midnight on Wednesday.
Fire and Emergency said that meant no open-air fires were allowed and all fire permits were suspended.
District Commander Dave Stackhouse said there have been several significant fires in Canterbury recently, and hot, dry, windy weather was expected to continue for the next two months.