Auckland recorded its hottest April temperature since 1998 yesterday afternoon.
The view from a beach on Waiheke Island. Photo: 123RF
Thermometers reached 26.5 degrees Celsius, 8C higher than the average for the month.
MetService meteorologist Tui McInnes said the humidity was caused by a tropical air mass over New Zealand.
Temperatures have been higher than usual in the North Island but should drop overnight.
Meanwhile, motorists travelling in the South Island should prepare for possible flooding across roads and gusty winds following stormy conditions.
Drivers should delay journeys if possible.
Waka Kotahi said State Highway 6 and roads north of Westport were slippery after heavy rain this morning.
State Highway 67 from Fairdown to Waimangaroa north of Westport, SH6 south of Westport to Punakaiki and east of Westport to Inangahua also have flooding and slips.
Both Southland and the West Coast had their highways closed earlier.
A heavy rain warning is in place for Buller and Westland north of Otira until 1am tomorrow.
Gusty winds can be expected on the east coast and through the alpine passes.
More than 12,000 residents in Queenstown, Glenorchy and Frankton were without power after a lightning strike this morning.
By 12pm, Aurora Energy said power had been restored except for about 300 customers in the Frankton area, who were due to have their power restored shortly.
MetService said there were 286 lightning strikes over the South Island in a three-hour period.
Queenstown Lakes District Council said a slip has closed Glenorchy-Queenstown Rd at Boundary Creek (opposite Pigeon Island) for the day and an update will be provided at 3pm.
A slip on Glenorchy-Queenstown Rd at Boundary Creek (opposite Pigeon Island). Photo: Facebook / Queenstown Lakes District Council