"It all depends on how much moisture there is over the weekend."
He said if there was a more northerly flow, it would bring more cloud.
There is also an area of high pressure coming from the southern east coast of the country that would influence the variation of weather across the country. So far the summer in Wairarapa has been up and down but today looks to be a true summer's day with mainly fine weather and a 26C high.
The east of the North Island is the only part of the country that could have above average temperatures this summer, according to National Institute of Water and Atmospheric Research.
December to February temperatures in the region are likely to be average or above average while the rest of the country's temperatures are most likely to be average.
Most of the main centres aren't looking too hot for Christmas Day, with many expecting rain, showers or cloud.
Wellington is expected to be partly cloudy with northeasterlies and a high of 17C.
Christmas Day in New Zealand can be a hit and miss affair, weather wise, according to historical data.
The hottest Christmas Day in Masterton was in 2012, when the mercury hit 30.4C and the coldest in 1999, at just 13.5C.
Wellington's hottest day was in 1934 with a high of 28.7C.
