Parts of the South Island have dropped to their lowest temperatures in over 40 years as a massive high-pressure system send the mercury plummeting.
NIWA Weather says the small Otago town of Middlemarch hit -12.3C early on Sunday - New Zealand's coldest June temperature since 2015 and the settlement's lowest since 2001.
To the west, Clyde dropped to -9.9C - its lowest since 1978. Next on the list were Ranfurly (-9C), Alexandra (-8.2C) and Lauder (-7.9C).
The freezing temperatures have been caused by one of the strongest areas of high pressure on the planet moving over the top of the South Island, bringing with it clear skies and light winds. This prevents the heat from being locked in, allowing it to escape into the atmosphere.
The result has been some savage frosts, with both the South Island’s interior and highlands and the lower inland part of the North Island and Central Plateau waking up to white grass and frozen water.
By Monday night and into Tuesday a sub-tropical flow will move in making for warmer-than-average overnight lows, meaning the South Island goes from several degrees below normal to several degrees above normal in just 48 hours.
MetService warns rain is expected about western parts of the South Island during Monday and Tuesday, with the heaviest accumulations about the ranges of Westland, Buller and northwest Nelson. Watches are now in force.
