Warm winter temperatures will likely stick around for a few more days - but forecasters warn not to get used to them.

The country's had temperatures in the late teens, some parts posting 20 degrees - which WeatherWatch's Philip Duncan said is very warm for this time of year.

But he said the cold snap the country's been waiting for is right around the corner.

"We'll see big, cold, wintry southerlies coming back to the country. So, this warm weather may last for the rest of June but it may not continue through the rest of July."

He said there's been isolated downpours across the North Island overnight.

"But also around Nelson and around the west coast of the South Island too as this big low from the Tasman Sea slowly starts to move in towards the central part of New Zealand."

Duncan said the storms, caused by sub-tropical air, are squally and hard to pinpoint - but could result in some extra water on some of the country's low-lying roads.