The ridge will force cloud to blanket western and inland areas of the country and will restrict overnight temperatures from dropping too dramatically.
Metservice meteorologist Tui McInnes said the forecast for many remains chilly despite the ridge of high-pressure moving over New Zealand.
"Meteorologists often refer to this situation as a 'dirty ridge'," he said.
"The anticyclone effectively traps moisture beneath it, restricting how it can move around in the atmosphere."
"The end result is more persistent cloudy conditions, especially during the morning and evening."
McInnes said some frosts are possible and Kiwis around the country can expect a few "nippy mornings".
WeatherWatch said the high-pressure ridge will run for several thousand kilometres from west to east but not very tall from north to south.
"This particular set up means there is a westerly flow across New Zealand, even if very light, for much of this week and that encourages clouds off the Tasman Sea," they said.
"These clouds are low-altitude ones which means then stop when they reach the ranges and higher level ground across NZ.
"This cloud makes for cooler days as it limits sunshine but milder nights as it helps hold on to the daytime warmth."
