Mr Kerr said northwesterlies would probably bring rain to western and southern parts of the South Island in days ahead.
There could even be a risk of heavy rain in the upper North Island later on Friday and early Saturday, as a frontal band reached that area, Mr Kerr said.
In the South, could southwesterlies on Friday would likely bring snow to lower than usual altitudes in eastern and southern areas.
WeatherWatch said this week would remind New Zealanders spring had arrived, with warm winds pushing highs into the low 20s.
The week would be a positive one for farmers, WeatherWatch said.
Warmer than usual temperatures should be a boon to farmers who had suffered from below-average soil temperatures.
Tomorrow, eastern areas of both islands would be warmest, WeatherWatch said.
Rain or showers were likely to affect the South Island's West Coast for most of the week, clearing on Friday.
Tomorrow's forecast:
• Whangarei: Cloudy spells, light showers possible, southwesterlies develop. Low 9C, high 16C
• Auckland: Cloudy spells, southwesterlies develop. Low 11C, high 15C
• Hamilton: Cloudy periods. Westerly breezes. Low 7C, high 14C
• Tauranga: Cloudy periods. Southwesterly breezes develop. Low 10C, high 16C
• Wellington: Fine. Northwesterly gradually freshens. Low 11C, high 15C
• Christchurch: Fine with high cloud. Northwest strengthens in evening. Low 6C, high 20C
• Dunedin: Partly cloudy. Northwest strengthening in afternoon. Low 11C, high 19C
(Source: MetService)