An enormous high pressure system (anticyclone) has been affecting New Zealand for 10 days now and will continue to do so for another 24 to 48 hours before finally slipping away out to the east.
As it slides off the South Island late Wednesday it will allow a much cooler change to move in on Thursday and Friday with some regions in the South Island losing 10 to 15 degrees off their recent afternoon temperatures. The cooler change reaches Wellington on Thursday PM and then the eastern North Island over Friday, lasting just one day.
The more unsettled pattern means there will be some heavy rain around New Zealand this week but it will be hit and miss. The North Island does remain mostly dry but may see some heavy downpours on Saturday in dry northern areas – but without any cool down.
Saturday’s rainfall potential in the North Isand is not yet included in the rainfall accumulation maps below.