An "enormous" 9000km-wide anticyclone is heading towards New Zealand - and it's going to bring grey, cold and gloomy weather.
Weather Watch head weather analyst Philip Duncan told Newshub it's one of the largest highs he's ever seen.
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"A truly massive belt of high pressure will this week influence New Zealand's weather starting today and not leaving until next Tuesday (eight days from now)," WeatherWatch says.
"It is by far the largest high pressure system in our part of the world so far this year."
An anticyclone is the opposite of a cyclone - it's a weather system with high pressure at its centre.
Duncan says it's going to bring cloud and showers to the western areas of the country. This cloud makes for cooler days as it limits sunshine but it also means milder nights as it helps hold on to the daytime warmth.
"Anticyclones don't always bring sunny weather and the huge high this week is no different with gloomy weather expected across western regions in particular," he says.
"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.
"These clouds are low altitude ones which means then stop when they reach the ranges and higher level ground across NZ."
On the other side, eastern areas will often be mostly sunny as the main ranges block the lower level clouds coming in from the west.