Mean sea level pressures were higher than normal over the southern South Island and to the south, east and west of the South Island in June 2018. In contrast, near normal mean sea level pressure was observed over and to the north of the North Island. This pressure setup resulted in anomalous easterly and south-easterly winds over New Zealand during June, a pattern that was generally reflected in the rainfall anomalies: dry in the west and wet in the east.
Temperature
Temperatures varied during June across the country. It was a warmer than usual June for the north and east of the North Island, but much of the South Island and the southern North Island recorded below normal temperatures for the month. Mean temperatures for the eastern South Island were warmer than usual, a consequence of persistent cloud and resulting in well above average nocturnal (minimum) temperatures. However, the stubborn cloud also resulted in below average daytime (maximum) temperatures. Overall, minimum temperatures were most unusual, resulting in above average mean temperatures. Towards the end of June, several snowfall events and southerly airflows sent temperatures tumbling downwards for much of the country.
Rainfall
There was a striking difference between western and eastern areas in terms of rainfall for June. The northern and eastern North Island and northeastern South Island bore the brunt of numerous heavy rainfall events from the east. Much of this area received over one-and-a-half times their usual June rainfall, with over 200% of normal June rainfall recorded in some locations. In stark contrast, most of the remainder of the South Island, as well as Taranaki, experienced well below normal rainfall, with less than half of the usual June rainfall falling for much of the South Island.
Soil Moisture
As of 1 July 2018, soil moisture levels were above normal for the time of year for eastern and central parts of the South Island north of Southland, and the Hawke’s Bay. Soil moisture levels were generally near or slightly above normal for the time of year across the remainder of the country.
