Warmer days and nights are likely across eastern and northern Australia, with cooler days and nights more likely in Tasmania and south-west WA, the Bureau of Meteorology says.

There is a particularly high chance of summer having a warm start for most, with much of Australia likely to see warmer daytime temperatures in December.

Below average rainfall is predicted in parts of the east and above average in northwest WA.

The bureau says this outlook is strongly influenced by a climate driver called the “Southern Annular Mode”. It is expected to be in a negative phase in December.

When this happens in summertime, weather systems are further north than usual, meaning Australia experiences higher pressures than normal. This is typically associated with reduced rainfall and higher temperatures.

The Pacific Ocean is tilting slightly towards La Niña, increasing sea surface temperatures in the western Pacific Ocean, including around northern Australia.

This may be raising the likelihood of increased rainfall over northwest WA during summer.