New Zealand is now under the influence of a large high pressure system coming in from the Tasman Sea. Dry weather will persist for a few days ahead over most areas, before a sharp cold front brings widespread rough winter weather from Saturday night and across Sunday. Some light coastal showers will persist in both islands.
Wednesday will be a beautiful sunny day in most areas of the country after a cold start, where Auckland had frosts in sheltered places and an overnight low near 0 degrees, while just down the road Hamilton had -3C.
For Wednesday the exception for sunny weather is mostly Southland, where persistent southwesterly winds bring low clouds and maybe light showers. Clouds with southwesterly winds may also spread over coastal areas in Wellington and Gisborne – but as you can see from the first InfoGraphics (below) the wind flow is moving the same angle as the country lies (south west to north east) and so these coastal showers will affect both west and east coastlines at various times as this air flow adjusts itself around the incoming high. A slight shift from SW to SSW can shift showers from west coast to east coast!
Thursday will then be sunny in Wellington, Christchurch, and most areas in the South Island except Southland once again. Cloud cover will increase in Taranaki, Waikato, Auckland and Northland from Thursday morning as winds shift just a little.
Due to the recent cold southerlies and now clear skies (especially inland) minimum temperatures during nighttime will be lower than normal for next few days, especially in the North Island and upper South Island. Sub-zero minimum temperatures are possible in wide areas over interior North Island, rising the risk of frost. Coastal areas have more of a breeze and clouds which may keep temperatures above zero for the most part.