A negative IOD often results in more rainfall than average over southeastern Australia. The map below shows rainfall during negative IOD years is generally above average (decile 8 or higher, indicated by the blue shading) across the mainland's southeast. In no part of the country is there a tendency towards below-average rainfall (decile 3 or lower, indicated by the red shading).
The temperature deciles maps show the typical maximum (left) and minimum (right) temperature impacts during a negative IOD. A negative IOD often results in cooler than average maximum temperatures (decile 3 or lower, indicated by the blue shading) over southeastern mainland Australia. Maximum and minimum temperatures in the far north are typically warmer than average.
The decile maps above are composites of 11 negative IOD years since 1960. The maps provide guidance on the typical conditions to expect during a negative IOD. For each of the 11 years, the deciles for the winter–spring period are calculated against all years between 1900 and 2019 for the rainfall map, and 1910 and 2019 for the temperature maps. These deciles are then averaged for each point in Australia, and the result mapped. Rainfall and temperatures for all negative IOD events may not follow an identical pattern, and areas of below-average rainfall and above-average temperature can still occur during a negative IOD.