Climate outlook for July to September

Issued 30 June 2016

Climate outlook overview

Most locations are likely to see above average rainfall this July to September.
Warmer days are likely in the tropical north and Tasmania, while cooler days are likely elsewhere.
Warmer nights are likely in the tropical north, eastern Victoria and Tasmania. Elsewhere across the southern mainland, cooler nights are more likely.
This outlook is influenced by a developing negative Indian Ocean Dipole in the tropical Indian Ocean and a tropical Pacific Ocean that is expected to cool towards La Niña levels. Very warm sea surface temperatures surrounding northern and eastern Australia are also influencing the outlook (see the Climate Influences section).

July to September rainfall is likely to be above average across most of Australia. However, southwest WA and western Tasmania have roughly equal chances of a wetter or drier three months.
July is likely to be wetter for most of Australia, except southwest WA.
The current outlook reflects the combination of a developing negative Indian Ocean Dipole, a continued cooling of tropical Pacific Ocean sea surface temperatures, and very warm sea surface temperatures surrounding northern and eastern Australia.
Historical outlook accuracy for July to September is moderate over most of Australia, but low in parts of the tropical north, near the WA border and central SA.

Cooler than average days are more likely for most of the country for July to September. Warmer than average days are more likely for the tropical north and Tasmania.
Night-time temperatures for most of the southern mainland are more likely to be cooler than average. Warmer than average nights are more likely across the tropical north, eastern Victoria and Tasmania.
The current outlook reflects the combination of a developing negative Indian Ocean Dipole, a continued cooling of tropical Pacific Ocean sea surface temperatures, and very warm sea surface temperatures surrounding northern and eastern Australia.
Historical maximum temperature accuracy for July to September is moderate to high over most of Australia. Minimum temperature accuracy is moderate over northern Australia and Tasmania, but low elsewhere.

The tropical Pacific has returned to a neutral ENSO state, following the 2015–16 El Niño. By July, climate models and observations suggest that conditions in the Pacific may approach La Niña thresholds.
Sea surface temperatures across the eastern half of the Indian Ocean and near northern and eastern Australia are above average. These waters near Australia have warmed as the 2015–16 El Niño event ended. These warmer waters may provide extra moisture for rain-bearing systems as they cross Australia.
A negative Indian Ocean Dipole (IOD) is developing in the tropical Indian Ocean. Negative IOD events typically enhance rainfall across southern Australia during winter and spring. However, this influence may be opposed by a predicted increase in mean sea level pressure to the south of Australia. Consequently, southwest and far southeast parts of Australia have roughly equal chances of a wetter or drier three months.
It should be noted that it is seasonally dry at this time of year over the tropical north of Australia. The median rainfall at many tropical locations is between 0 and 1 mm for July to September, so even a small amount of rain would exceed the median.
Bureau climatologists continually monitor the climate for any significant developments, with information on El Niño/La Niña and IOD events available fortnightly via the ENSO Wrap-Up. For a summary of Pacific and Indian Ocean outlooks, please see the Climate Model Summary.