Duncan said places like Dunedin, which had low-level snow within the past week, will head for highs of 14 while spots inland, such as Queenstown, which dropped to double negatives last week, will this week drop to a maximum low of about -2C.
Duncan said the week ahead would be a great week for skiers and snowboarders too - and for farmers in the north and west looking for a break in the rain.
The balmy forecast is a stark contrast to this time five years ago when the country saw its most severe snowfall since 1976, a once-in-a-generation weather event that stopped mail, cancelled buses and closed schools.
Temperatures in Wellington peaked at 6.8C on August 14, 2011, with ice making many roads impassable. In the north, a handful residents were hospitalised after strong winds brought down trees and power lines. In the south many homes and businesses were entirely cut off, with flights grounded in Christchurch, Queenstown and Dunedin.
But the winter wonder also brought excitement and joy - the Beehive was blanketed in white, children everywhere delighted in making snowmen in their backyards, and the next day on August 15, Aucklanders were amazed to see snow flurries on Queen St.
This week in the main centres
Auckland
Today - Fine with a high of 14C and overnight low of 6C
Tomorrow - Fine with a high of 14C and overnight low of 6C
Wednesday - Fine with a high of 16C and overnight low of 7C
Wellington
Today - Fine with a high of 14C and overnight low of 7C
Tomorrow - Fine with a high of 13C and overnight low of 7C
Wednesday - Fine with a high of 13C and overnight low of 7C
Christchurch
Today - Partly cloudy with a high of 12C and overnight low of 0C
Tomorrow - Fine with a high of 14C and overnight low of 1C
Wednesday - Fine with a high of 15C and overnight low of 2C