Key Points:

A MetService weather station at Whenuapai Air Base has recorded the hottest temperature reading ever in Auckland.

Temperatures peaked at 32.4 degrees Celsius during the 3pm hour, equalling the previous high recorded in the Auckland Domain in February 1872 - 137 years ago.

Niwa climate expert Jim Salinger said today's reading was the highest since official Niwa records began in September 1868.

Auckland's previous temperature high this year was 28.2 degrees, on the North Shore earlier this month.

Weather analyst Philip Duncan says the extra hot weather was due to a sudden clearance of cloud in the skies along with a gusty northwest wind.

He says's thermometer in west Auckland recorded 34 degrees, fuelled by the hot northwester.

Mr Duncan says although humidity is lower today, the intense heat and sunnier skies means it feels much hotter - and a humidex reading of 38 was recorded.

South Island weather analyst Richard Green says far from Auckland's high, Christchurch is having its second coldest day of the summer. It was 12.8 degrees around 6pm and still raining.

Mr Salinger warned temperatures would be much cooler in Auckland with the arrival of wetter conditions during Friday and over the weekend.